Gov. Gavin Newsom’s endorsement of Vice President Kamala Harris for the Democratic presidential nomination confirmed a foregone conclusion: Anyone hoping to see the governor in the White House should put those dreams on ice.

“Tough. Fearless. Tenacious. With our democracy at stake and our future on the line, no one is better to prosecute the case against Donald Trump’s dark vision and guide our country in a healthier direction than America’s Vice President,” Newsom posted on X, hours after Biden announced his decision to step down on Sunday and endorsed Harris as the Democratic nominee.

Biden’s choice to elevate his vice president to the top of the ticket makes sense for the party, and Democratic leaders across the nation quickly rallied behind her.

Endorsements from Newsom, Michigan Gov. Gretchen Whitmer, Illinois Gov. JB Pritzker, Secretary of Transportation Pete Buttigieg, Pennsylvania Gov. Josh Shapiro and others considered top Democratic presidential contenders all but guarantee a smooth nomination and a November showdown with former President Trump.

But the accession of Harris raises questions about Newsom’s political future. A top surrogate for Biden, Newsom’s support for the campaign may look different with Harris leading the charge for Democrats.

Unlikely to nab a VP spot

Newsom probably isn’t at the top of Harris’ list of vice presidential candidates.

A provision in the U.S. Constitution prevents electors in California from voting for a president and vice president from their own state. So for Newsom to join the ticket and be eligible to receive all 54 electoral college votes from the Golden State for a vice presidential run, either he or Harris would need to register to vote in another state.

When selecting a vice president, presidential nominees also often look for a prospect from a swing state that they might otherwise lose, said Jack Pitney, Roy P. Crocker Professor of Politics at Claremont McKenna College. Harris is already expected to win California, where Trump remains extremely unpopular.

“I think Josh Shapiro is very near the top of the list for that reason,” Pitney said about the Pennsylvania governor. “He actually could add a point or two.”

Among the most important factors, which Pitney defines as the “civics textbook criterion,” is to pick someone qualified to take over as president on Day 1.

“It turns out to be important, because if a candidate had serious questions about the running mate’s qualification, eventually, that lack of qualification is going to be obvious to the public,” Pitney said. “Classic case: Sarah Palin.” (Palin is the former governor of Alaska who was chosen as Republican John McCain’s vice-presidential running mate in 2008.)

A Harris win could delay Newsom’s White House prospects

Shay Franco-Clausen, a California delegate from the Bay Area who backs Harris, said Newsom or anyone else challenging the vice president as the nominee “would have caused more harm” following weeks of controversy over Biden’s disastrous debate performance and questions about the 81-year-old president’s ability to serve a second term.

“Look, we only have a little bit of time to win and so we needed to unify behind the party leader,” Franco-Clausen said.

“She’s already been vetted. She’s the only person that can take over the campaign finances. To step down and to uplift her and endorse her was just the message our nation needed.”

A Harris win in November could put Newsom on a long path to the presidency if he wants to run in the future.

Harris likely would run for reelection in 2028 and Newsom has said he would not compete against her in a presidential contest. That means he would have to wait another four years to take his shot.

Under that scenario, Newsom could have a lengthy lull between the time he terms out as governor in 2026 and launches a 2032 presidential campaign. Without an elected post, it could be harder for Newsom to stay relevant.

But others have done it, including President Reagan — who also served as California governor, Pitney said.

“Reagan was elected president six years after he left the governorship of California and we’ve seen over the years a number of candidates who have been successful even though they weren’t currently holding office,” Pitney said. “In some ways, it’s an advantage, because you don’t have to worry about a day job.”

The double-edged sword of a Trump win

A Democratic loss in November could end Harris’ political career and open the door for Newsom, or someone else, to grab the Democratic nomination in 2028.

If Trump wins, Newsom’s last two years in the governor’s office would be spent in a high-profile battle with the White House over California’s progressive policies and Trump’s conservative agenda.

The return of the legal battles and social media showdowns over immigration, climate change and healthcare that dominated the first two years of Newsom’s governorship could elevate his profile and leave him in a prime position to run for president in 2028.

“He’s obviously going to run against the Trump record and I’m sure four more years of Trump would give him a lot of ammunition,” Pitney said.

Newsom’s support for the ticket could look different than before

As a top surrogate for Biden, Newsom campaigned for the president in battleground states, such as New Hampshire, Pennsylvania and Michigan, earlier this month.

To the political left of the president, the governor’s visits helped to energize more progressive and younger voters. Newsom also acted as an attack dog for Biden at the GOP presidential debate last year and deflected criticism of Biden’s troubling performance after the president’s debate against Trump in June.

But the Harris campaign may not need to use Newsom the same way. While the Biden campaign embraced him, there’s the possibility that he could also be seen as stepping on Harris’ toes.

“This is a difficult situation,” Pitney said. “It’s no secret that they’ve had something of a rivalry for many years, but he understands that the best course for him is to be very supportive of the ticket.”

In a fundraising email sent on behalf of U.S. Senate candidates on Monday, Newsom repeated his endorsement of Harris and said he intends “to spend the next several months working to defeat Donald Trump and elect Democrats everywhere.”

“I have already visited a number of states campaigning for Joe Biden and many other Democrats and state parties,” the email said. “That work won’t stop.”