Pennsylvania Gov. Josh Shapiro, Minnesota Gov. Tim Walz and Arizona Sen. Mark Kelly are reportedly among the top contenders to be Vice President Kamala Harris’ running mate.

She’s expected to make her decision ahead of a campaign rally in Philadelphia on Tuesday.

Here are key things to know about each of the possible candidates:

Josh Shapiro: Shapiro, who was previously the state’s attorney general, was elected in a landslide victory in 2022, defeating a 2020 election-denying far-right state senator to become the third Jewish governor elected in the crucial swing state. During a stop in Philadelphia last month, Harris called Shapiro a “great partner to the president and me.” The assassination attempt against former President Donald Trump in Butler, Pennsylvania, placed the governor in the spotlight. His response to the death of Corey Comperatore, the Trump supporter who was killed while shielding his wife and daughter, has especially been lauded.

Tim Walz: Walz spent more than two decades in the Army National Guard, which included a deployment overseas after the 9/11 attacks, working as an educator and coach, before shockingly defeating a six-term Republican incumbent congressman in 2006, a wave year for Democrats. Walz remained when the tide rolled out, reelected to the typically red district repeatedly until he left to run for his current job in 2018. (The seat quickly returned to GOP control after his departure.) Walz’s six years in charge of Minnesota have seen a remarkable series of political and social upheaval. First came the Covid-19 pandemic and then, in its midst, the murder of George Floyd by a White police officer, which set off global anti-racist demonstrations. Walz navigated it all – alongside more usual complaints over wasteful spending – well enough that, by the beginning of 2023, he was leading a Democratic trifecta in the state government.