Hillary Clinton could have shared the Democratic presidential ticket with Bill Gates — or with his wife, Melinda. She could have named Michael R. Bloomberg, the billionaire former New York mayor, as her running mate. Or she could have chosen to reward a loyal friend and fund-raiser by making Gov. Terry McAuliffe of Virginia her No. 2.
All four were among the potential vice-presidential candidates Mrs. Clinton’s top campaign aides included in a first pass through their screening process, which turns out to have been well underway even before she amassed the delegates she needed to capture the nomination.
On March 17, just after Mrs. Clinton had defeated Senator Bernie Sanders in a string of primary contests, including those in Florida and Illinois, her campaign chairman, John D. Podesta, sent her a note of congratulations. “Ok, I can breathe again!” he wrote in a hacked email released by WikiLeaks on Tuesday. “Congrats on a fabulous night. I am feeling like it’s possible to get back to the longer term again.”
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Mr. Podesta updated Mrs. Clinton on the preparations for vetting potential running mates, including “nondisclosure agreements with anyone we involve in the process,” then rattled off a not-so-short list of vice-presidential prospects he and other aides had agreed to include in what he called a “first cut.”
“I have organized names in rough food groups,” Mr. Podesta wrote.
It was a balanced diet, indeed: Clustered below were the Latinos, women, white male politicians — including Mrs. Clinton’s eventual pick, Senator Tim Kaine of Virginia — African-Americans, military men, business executives and philanthropists.
Thirty-ninth and last on the list, and in a category all by himself, was Mr. Sanders.
The email, obtained by hackers who illegally breached Mr. Podesta’s account, appears to have kicked into gear a closely guarded vetting process that stretched on for months.
At the time, it was not yet assured that Donald J. Trump would lock up the Republican nomination, and Mrs. Clinton’s aides included running mates who could bolster the Democratic ticket should she find herself in a general election against Senator Ted Cruz of Texas or even Gov. John Kasich of Ohio.
Mr. Podesta’s list included many elected officials who were later reported to have been vetted, including the Obama administration cabinet secretaries Julián Castro, Tom Perez and Tom Vilsack, and Senators Elizabeth Warren, Sherrod Brown, Cory Booker and Michael Bennet.
But other potential running mates — including the chief executive of Apple, Tim Cook, Muhtar Kent, the Turkish-American chief executive of Coca-Cola, and Howard Schultz, the chairman and chief executive of Starbucks — would have been highly unconventional.
In the end, of course, Mr. Trump settled on Gov. Mike Pence of Indiana as his running mate, and Mrs. Clinton faced little pressure to respond by demonstrating unpredictability or boldness with her own choice.