(CNN)In a critical mark of the shifting political landscape, Democrats in November could secure a clean sweep of the Senate seats from the four key Southwestern states -- a milestone the party hasn't reached in nearly 80 years.
Democrats today are strongly positioned to oust Republican Sens. Martha McSally in Arizona and Cory Gardner in Colorado and hold their own open seat in New Mexico. If the party wins those three races, as most analysts today agree they are favored but not assured to do, it will control all eight Senate seats from Arizona, Colorado, New Mexico and Nevada for the first time since 1941, according to Senate records.
The Democrats' potential clean sweep of those Southwestern US Senate seats marks another advance in a tectonic remaking of the electoral battlefield. Even as Democrats struggle to maintain their position in slow-growing, predominantly white and heavily blue-collar battlegrounds across the Rust Belt, they are growing more competitive in the fast-growing, diverse and increasingly white-collar new swing states across the Sun Belt.
"There's no question now that the Democrats' path to a Senate majority runs through the Sun Belt," says Democratic consultant Robby Mook, the manager for Hillary Clinton's 2016 presidential race. "We've got to be winning there to succeed. And increasingly the same is going to be true for the White House."
"One way to put it," Mook says, "is the blue wall is retiring to Phoenix."
Although the politics of each state varies, the most common thread is that Democrats are rising across the region based on their strength with growing populations of college-educated white voters and nonwhites (especially Latinos), most of them concentrated in large metropolitan areas, including Denver, Phoenix and Las Vegas.
"The Democrats are going to be a southern party again, but it's going to be a very different southern part of the country that has been remade into the Sun Belt and includes very large metros with diverse populations," says Robert Lang, a professor of urban affairs at the University of Nevada at Las Vegas and co-author of "Blue Metros, Red States," an upcoming book on the large metropolitan areas of the Sun Belt.
Since then, less than two weeks after the US entered World War II, Democrats have never controlled all eight of the region's Senate seats. Nor, since Truman in 1948, have they won all four states in a presidential race. Republicans more recently carried all four in each presidential contest from 1968 through 1988, as well as in 2004. In the past three elections, Democrats have won New Mexico, Nevada and Colorado each time. But they have carried Arizona only once since 1948 (when Bill Clinton won it with less than half the vote in the three-way 1996 race), though Hillary Clinton significantly narrowed the GOP margin there to 3.5 percentage points last time.
Who's in the running
In New Mexico, Democratic Rep. Ben Ray Lujan will run against the winner of a June Republican primary to succeed retiring Democratic Sen. Tom Udall.
While the Southwestern states are fabled for their picturesque wide-open spaces, the growth in Colorado, Arizona and Nevada has been propelled primarily by a single large metropolitan area in each state that dominates the economy.
In Colorado, the Denver metropolitan area accounted for just over half of the state's votes in the 2016 presidential race and an even larger share of its jobs (almost 55%) and total economic output (just over three-fifths), according to figures compiled by Lang and UNLV political scientist David Damore in the upcoming "Blue Metros" book.
In Arizona, the Phoenix metropolitan area accounted for nearly two-thirds of the state's 2016 votes and about three-fourths of its jobs and economic output. In Nevada, Las Vegas similarly provided two-thirds of the state's votes in 2016 and nearly three-fourths of its jobs and economic output.
Only New Mexico departs from this pattern, with Albuquerque, its largest city, accounting for only about one-third of the state's votes.
In important ways, the metros are being reshaped by common experiences. All are adding population: The Census Bureau recently reported that Phoenix added more people than any other US city from 2010 through 2019. All contain large numbers of racial minorities, particularly Latinos. And all are enjoying substantial in-migration from other states, especially California, which in 2018 alone exported over 68,000 people to Arizona, more than 50,000 to Nevada and nearly 29,000 to Colorado, according to census figures.
In other ways the three diverge. Phoenix and Denver are adding legions of white-collar jobs for well-educated young professionals in health, energy, computer software and other industries; the Las Vegas workforce, which revolves around the gambling industry, isn't nearly as well-educated or well-paid. On the other hand, organized labor, which provides a strong organizing boost to Democrats, is a much more powerful presence in Las Vegas than in the other two.
Yet all these differences net out to a common political dynamic: Even as these three metro areas are growing in size, they are also growing more Democratic in their voting behavior. That means Democrats are winning a bigger share of an expanding pie -- a compounding risk for the GOP.
"It's not just urban, it's suburban" communities that are shifting in their votes, notes Mook. "It's culturally that the suburbs are rebelling against Trump and Republicanism, and these are the parts of the country where those suburbs are blowing up in size. It's like double trouble for the Republicans."
Since the early 2000s, that pattern has transformed Colorado from a red state that leaned Republican to a truly purple battleground to a state that now demonstrably tilts toward the Democrats.
In the 2004 presidential race, while winning Colorado, George W. Bush won the big suburban Denver counties of Arapahoe and Jefferson and emerged from the Denver region (which also includes Denver itself and Adams County) with a manageable deficit of about 76,000 votes. By 2016, Trump, while losing the state, lost all four of those counties by a combined margin of about 200,000 votes; in 2018, Democratic Gov. Jared Polis won those four by fully 300,000 votes in his landslide victory.
The concern for Republicans
The shift of the large metros also keyed the 2018 Democratic Senate gains elsewhere in the region that positioned them to potentially achieve their historic sweep come November.
In Arizona, Maricopa County, which balances a large population of Latinos, white-collar white suburbanites and generally conservative white retirees, has not tilted nearly as reliably toward Democrats. But it appears just to be a few elections behind on a similar trajectory to Denver and Las Vegas. Maricopa was the largest county in the US that Trump won in 2016, when he carried it by almost 45,000 votes. But in 2018, Democrat Kyrsten Sinema carried Maricopa by 60,000 votes en route to her narrow statewide victory.
Both parties agree that Gardner and Trump today are facing even larger deficits in the Denver area than in their last races, particularly among well-educated voters. In each case, Trump and the GOP Senate contenders hold solid advantages in the small-town and rural communities that have flocked to his culturally polarizing messages and also generally faced less impact from the coronavirus outbreak. But if the populous metro areas move decisively against the GOP, Lang notes, "you quickly run out of rural voters to reverse it."
Republicans across the region acknowledge that if they "can't stop the bleeding" in the large metro areas, as Nicole McCleskey, a GOP pollster based in New Mexico, puts it, the Southwest will continue to drift away from them. But while Trump's tempestuous personality and behavior have complicated the challenge of holding suburban voters, Republicans believe that party positions such as resistance to taxes and strong border enforcement still offer them opportunities to recapture more of them.
"I think you have a range of issues there are more hospitable to Republican candidates," McCleskey says.
In Colorado, Richard Wadhams, the former state GOP chair, acknowledges that Trump has alienated many of the young professionals swarming into Denver for well-paying information-age jobs. But he holds out hope that Republicans can regain at least some of those voters by focusing their attention on the prosperity that they enjoyed before the outbreak.
"They don't like Trump," he says. "But when they really have to choose in November, who is really going to get this economy going again, they know what it was like for three years when Trump was President before all this broke. Those young professionals who moved here might be a little skeptical of a Biden presidency with a Democratic-controlled Congress."
The worries for Democrats
Even more concerning to them are signs that Biden has so far failed to connect with many younger Latino voters. Among Latinos in the region, "we are not where we need to be," says Stephanie Valencia, co-founder and president of EquisLabs, a Democratic polling firm focusing on Latino voters. Large numbers of Latinos younger than 50 are ambivalent at best about Biden, she says, and uncertain to turn out in November.
"With the Latinas the support is there; the question is how do you get them to come out," she says. "With these ambivalent young men, [the question is] how do we get them to care at all?"
Despite these potential hurdles, political observers in both parties believe Democrats have a real opportunity to match their 1936 sweep, when they won all four states in the presidential race and controlled all eight of their Senate seats.
Arizona is the toughest of the four for Democrats, but Grant Woods, the state's former Republican attorney general, says he considers both Biden (who he has endorsed) and Kelly solid favorites to win by at least 3 to 5 percentage points. The OH Predictive Insights polling this spring has consistently found Biden solidly ahead with right around 50% of the vote and Kelly enjoying even wider advantages.
"I think Arizona is about a couple of election cycles behind Nevada in going blue," Woods said. "If the Republican Party wants to continue to push in the direction of being anti-education, and they want to be the party of ... the bigoted, then they are going to go down the drain in the Southwest, because that's not what the Southwest is. It's a very culturally diverse place that values education and is going in the opposite direction. You can see where [the politics] are going."
The scariest prospect for Republicans is that everything said above about Arizona and Colorado in particular could also apply to Texas, the foundation stone of the GOP's national political strength. From Dallas/Fort Worth and Austin down south through Houston and San Antonio, the four metropolitan areas in what's called the Texas triangle account for just over two-thirds of the state's votes and jobs and more than three-fourths of its economic output.
All of them rank among America's 10 fastest-growing cities, according to the census. (All are also big recipients of transplants from California, which sent over 86,000 migrants to Texas just in 2018.) And as they grow, they are shading more blue: In his narrow 2018 defeat, the Democratic Senate candidate Beto O'Rourke won the five counties encompassing those cities by nearly 800,000 votes, roughly six times then-President Barack Obama's combined margin just six years earlier.
Like other observers, Lang says that for now, the massive GOP advantage in Texas' rural areas should allow Trump to hold it in 2020 (albeit likely by a much smaller margin than his 9-percentage-point victory last time). Republican Sen. John Cornyn also looks tough to beat. But in both parties, many agree that the shift away from the GOP in the large metropolitan areas driving the state's population growth have placed Texas on the same political moving walkway as Colorado, Nevada and Arizona, only a few steps behind.
"There is no question in my mind that if everything continues on the current trajectory, Democrats are going to start winning Texas," says Mook. "That is a radical tectonic shift in the Electoral College math. That's like the Democrats losing California."
Republicans might disagree about the time frame for Democrats to flip Texas in presidential or other statewide races, but they don't disagree that the state is growing more competitive. That's why, as the GOP tries to hold the line this fall in Arizona and reverse its decline in Colorado, Nevada and New Mexico, it will also have a wary eye on the outcome in Texas, the behemoth of a region whose politics are transforming even as it swells in population and economic clout.