After Harris selected Walz as running mate, a look at the 2 men who came closest to being picked

When Gov. Josh Shapiro took the stage ahead of the newly minted Democratic ticket of Vice President Kamala Harris and Minnesota Gov. Tim Walz on Tuesday night in Philadelphia, Pennsylvania, he told the crowd -- made up of thousands of his constituents -- how much he enjoyed being their governor.

"I want you to know, every single day, I go to work for you," he said to loud cheers.

Shapiro, who had been informed hours earlier he would not be Harris' running mate, expressed the same sentiment in an earlier post on X after Harris announced her selection of Walz.

Indeed, Shapiro -- whose strong popularity in a critical swing state made him an instant front-runner to join the Harris ticket -- had concerns about leaving his role as governor, which he assumed just last year, a person familiar with the vetting process told ABC News.

The person cited Shapiro's "love" of the job and, notably, of being in an executive role, suggesting that playing second fiddle to Harris may not have been a good fit.

As it happens, Shapiro appeared to turn off Harris and her vetting team by inquiring too much about the specific roles he would play in an administration, according to reporting from CNN and the New York Times, an approach seen as too ambitious.

In a condensed vetting process to find Harris' running mate, in which the vice president's team looked into roughly a dozen candidates, just three ended up holding in-person meetings with Harris and her team Sunday in Washington, D.C.: Walz, Shapiro and Arizona Sen. Mark Kelly.

Kelly met with Harris for roughly an hour and "walked out of it feeling really good," a person with knowledge of his vetting process told ABC News, though Harris quickly appeared to narrow her options to Walz and Shapiro by Sunday night.

The near immediate emergence of Kelly's name as a possible running mate surprised his team, and the opportunity "fell out of the sky" for a former astronaut who had not run for elected office until 2019, the person said, adding that Kelly was "playing with house money."

That's not to say the senator appreciated being passed over, someone who knows him well told ABC News.

"He's a very competitive guy," said the person, who said they hadn’t spoken to Kelly since the Walz selection, but spoke out of familiarity with the senator on a personal level.

"He doesn't like losing."

During the two-week sprint to find Harris' running mate, the final vice presidential hopefuls received praise from Democratic strategists and elected officials -- but each endured negative headlines.

Shapiro received the brunt of negative attention when progressives attacked him relentlessly for what they perceived to be a lack of empathy toward pro-Palestinian campus protestors this spring. Shapiro, who is Jewish, encouraged University of Pennsylvania officials to disband a pro-Palestinian encampment this spring, though he has also been critical of Israel, calling Israeli Prime Minister Benjamin Netanyahu "one of the worst leaders of our time."

The governor was also challenged over his support for school vouchers and a nearly $300,000 settlement his administration entered into to resolve a sexual assault complaint against an ex-aide, who thereafter resigned.