Since taking over the top spot on the Democratic ticket from Joe Biden, Harris's campaign has surged, setting fundraising records and erasing Donald Trump's lead.
Pennsylvania Governor Josh Shapiro, a rising Democratic star, is widely seen as the leading choice for Harris's running mate, though Minnesota Governor Tim Walz and others, including Transportation Secretary Pete Buttigieg, are also in contention. Harris is expected to make her selection known via a video announcement.
On the eve of their swing state tour, Harris hinted at continued suspense over her choice, telling supporters in a text that she had not yet made a decision.
Harris, 59, and her new running mate will kick off their tour with a rally at Temple University in Philadelphia before visiting Wisconsin and Michigan on Wednesday, Arizona on Friday, and Nevada on Saturday. Events in North Carolina and Georgia on Thursday and Friday respectively have been postponed due to a tropical storm.
Shapiro, popular in Pennsylvania—one of the key swing states—could enhance Harris's prospects in these critical areas. As a potential first Jewish vice president, his selection would add to the ticket's diversity, though his stance on Israel has sparked some controversy among progressive activists.
Walz, a 60-year-old former National Guard officer known for his down-to-earth style, is seen as a liberal alternative and has gained attention for his critique of Trump.
Other possible picks include Arizona Senator Mark Kelly, Kentucky Governor Andy Beshear, and Illinois Governor J.B. Pritzker.
Harris began her search for a running mate after Biden's withdrawal from the race on July 21, driven by concerns over his age and declining popularity. Recent polls show Harris with a slight edge over Trump nationally, though her support among Black voters lags behind Biden's 2020 figures. Analysts caution that the race remains highly competitive.
"She has a lot of momentum, but the polling still indicates a tight race," said David Axelrod, former strategist for Barack Obama. "This will be a hard-fought battle for either side."