In choosing Kamala Harris, Biden selected the candidate who had been the frontrunner among political handicappers and betting markets for months. The senator from California fulfills Biden's pledge to name a woman and responds to the expectation that he would pick the first woman of color ever to serve on a national ticket.
Harris is a charismatic and telegenic politician. And as a US senator and recent presidential candidate, Harris also meets another important test for Biden. People familiar with research the campaign undertook to inform its decision told me voters viewed her as among the most qualified to be president on Day One -- a key positive, given Biden's status as potentially the oldest politician to ever serve as president.
She is also familiar with the maelstrom of a national campaign, having spent a year running for president, albeit unsuccessfully. Though she was at times less than sure-footed in dealing with incoming criticism from the media and opponents, she understands the pace and nature of it, which will only intensify in a fall race against Trump.
One of the principal tasks of a running mate is to play a lead role in bringing the case against the other ticket, particularly in the vice-presidential debate.
That exchange, in which Harris played up her own experience as a child who benefited from busing, briefly vaulted her to the top echelon of candidates in polling. It also was a source of friction with Biden and his family that could have upended his choice.
In the end, Biden seriously considered others but returned to Harris as the "do no harm" candidate, unlikely to thrill or outrage many. She may not seem the most comfortable fit as a governing partner, a quality Biden said he was seeking, but Harris was viewed as the safest pick to win in November.
By naming her, Biden likely also has set the dynamics for the 2024 election, not just the current one. The former Vice President has not said he would stand down after one term, though given the fact that he would be 81 by the next election, it is widely assumed he would not run.
This also will place Harris in not only an historic but a historically challenging position if the Biden-Harris ticket wins. She immediately would be installed as heir apparent and putative frontrunner for the Democratic presidential nomination four years from now.
That means she would become an immediate target for Republicans seeking to inflict political damage on the standard bearer they may face on the ballot in 2024. It also would challenge her to balance the roles of loyal and supportive vice president and candidate-in-waiting.
Balancing these pressures would be a challenge for anyone who assumed the number two spot under these unique circumstances, but perhaps even more so for Harris, 55, who already has sought the presidency and is presumed to still harbor that goal.
Others Biden considered may have fit more comfortably into partnership with him.
Harris has been publicly vetted, at least partially, through her race for the White House. And while Biden may have questions about how she would operate as vice president, he also knows that it will be a moot point if he isn't elected.
In making his choice, Biden signaled that he is focused like a laser on November, and he views Harris as the best bet to win.