The US vice-president, is expected to announce her selection by Tuesday, ahead of her first scheduled public appearance with her running mate that evening at Temple University in Philadelphia.

It was unclear if a final decision has been made, the sources said. The rally will kick off a five-day, seven-city tour of the battleground states likely to decide the November 5 election.

The choice of a running mate is one of the most consequential decisions of Harris’ political career, as she hastily pulls together a campaign to challenge Republican nominee Donald Trump and US Senator JD Vance, his vice presidential pick. Vance will also make a campaign stop in South Philadelphia on Tuesday.

Shapiro, 51, is a rising star of the party with strong approval ratings in Pennsylvania, whose 19 electoral votes makes it a must-win state for both Harris and Trump.

A former state attorney-general, Shapiro would add to the ticket’s historical significance; he would be the country’s first Jewish vice-president, while Harris is seeking to become the first woman and the first Asian American elected US president.

His strong support for Israel could alienate some progressive voters, though it could also appeal to moderate voters and defang Republican efforts to turn the Israel-Gaza war into a wedge issue for Democrats.

Walz, 60, is a US Army National Guard veteran and a former teacher who has raised his profile in recent weeks as an effective advocate for Harris. He has attacked Trump and Vance as “weird,” a viral insult the Harris campaign has embraced.

A former member of Congress from a Republican-leaning district, Walz has proven appeal to rural, white voters, though he has also championed progressive policies as governor, such as free school meals and expanded paid worker leave. While Minnesota is a solidly Democratic state, it borders Wisconsin and Michigan, two crucial battlegrounds.

Speculation had focused on six finalists – four governors, a senator and a cabinet secretary in the Biden administration, all white men with a record of winning over rural, white or independent voters.

In addition to Shapiro and Walz, the other contenders included US Senator Mark Kelly of Arizona, Transportation Secretary Pete Buttigieg, Kentucky Governor Andy Beshear and Illinois Governor JB Pritzker.

The candidates will be informed on Monday night or Tuesday morning whether they were picked, sources told Reuters. The Harris campaign plans a social media announcement featuring the duo, campaign officials familiar with the arrangements said.

Harris’ search for a running mate began in earnest two weeks ago, shortly after President Joe Biden withdrew from the race and endorsed her to replace him.