Over the past four months, Gavin Newsom, the Democratic governor of California, has traveled to six Republican-led states. He has goaded Gov. Ron DeSantis, the Republican presidential candidate from Florida, to debate on Fox News. He has assembled a small staff of political advisers and created a political action committee to distribute $10 million to Democratic causes and candidates.
And this week, he raised $40,000 for a long-shot candidate for the United States Senate in Tennessee, one of the red states he has criticized his own party for neglecting.
By all appearances, Mr. Newsom is a man with an eye on the White House, building a national network of supporters and accumulating the kind of good will among donors, party operatives and voters that could prove critical should he decide to move beyond Sacramento. Mr. Newsom said in an interview that he was not running for president, and that the time has come for Democrats to rally around President Biden.
“The train has left the station,” Mr. Newsom said. “We’re all in. Stop talking. He’s not going anywhere. It’s time for all of us to get on the train and buck up.”
But it may be difficult for Mr. Newsom to quiet speculation about his own future. He has spent months positioning himself as one of his party’s leading voices during a time of deep Democratic worry and lingering unease about the political strengths of Mr. Biden, who is 80, and his vice president, Kamala Harris.
A CNN poll released on Thursday found that 73 percent of all respondents were “seriously concerned” that the president’s age might affect his mental and physical competence. Some 67 percent of Democrats said the party should nominate someone else.
Mr. Newsom has, by his account, sought to reassure the White House in both public and private that he is no threat to Mr. Biden’s re-election campaign. And in turn, Mr. Biden’s team has appeared to pull him closer. The governor will be a top Democratic surrogate defending Mr. Biden when Republican candidates debate at the Ronald Reagan Presidential Library later this month.
This dance — of raising one’s profile without undercutting the president — is the challenge for a class of Democrats-in-waiting, which also includes Gov. J.B. Pritzker of Illinois and Gov. Gretchen Whitmer of Michigan. But Mr. Newsom, a 55-year-old telegenic, popular-in-his-own-state leader, has made himself the most visible in this group, and he may serve as a reminder of Mr. Biden’s shortcoming as he seeks re-election.
“He’s got to be careful about it,” Joel Benenson, a pollster who advised Barack Obama and Hillary Clinton, said of Mr. Newsom’s effort to raise his profile. “You don’t want to be too cute by half. If you are going to run, do it. If not, go out there and make the connections and talk to Democrats, learn about these states. The worst mistake would be the way to do it and seem sly about doing it.”
Mr. Newsom presents his travel to Republican states as an attempt to build up the Democratic Party in places he argues it has neglected. And while defending Mr. Biden, particularly on questions about his age and fitness, he also engages in a debate over cultural issues — transgender rights and gun control, to name two — that Democrats have sometimes avoided.
Mr. Newsom spent nearly an hour with Sean Hannity on Fox News in June to make the case for Mr. Biden and to defend his own record in California. “You have to give Gavin Newsom a lot of credit,” Mr. Hannity said in an interview. “He knew it wasn’t going to be an easy interview.”
Mr. Newsom recently turned up at a Boise, Idaho, bookstore to denounce “the insane book bans happening across the country. ” He has picked arguments with Republican governors like Mr. DeSantis of Florida and Greg Abbott of Texas, on abortion, gun control and trans rights.
“He is taking the fight to the Republicans,” said Jared DeLoof, the executive director of the Democratic Party in Idaho, where Mr. Newsom appeared in July. “Too often Democrats shy away from things like critical race theory or transgender rights or some of these issues that Republican like to pop off about. The governor showed he was really effective on this issues — we can take them on, and we can win.”
Mr. Newsom said his activities were done with the consultation and approval of the White House, an assertion confirmed by White House aides.
“I am sensitive to that,” he said, noting that he has made a point of not visiting states that are at the center of the presidential battleground. “I am trying not to play into the presidential frame.”
(Mr. Newsom, however, did suggest that his still-unscheduled debate with Mr. DeSantis take place in, among other states, Nevada and Georgia, both of which are likely to be in play in 2024.)
A spokesman for Mr. Biden’s re-election campaign, T.J. Ducklo, said in a statement Friday that Mr. Newsom had “forcefully and effectively makes the president’s case publicly and is an enormous asset to our fund-raising and organizing operations.”
There are other potential sources of friction as Mr. Newsom’s profile rises. Mr. Newsom and Ms. Harris are both ambitious Democrats from the same state who are of similar ages — she is 58 — and have, over the years, had to navigate around each other as they traveled down the same political roads. Ms. Harris would almost certainly be a rival in a Democratic presidential primary in 2028.
Mr. Newsom said he and Ms. Harris speak regularly and rejected the suggestion that his success comes at her expense. “This is a true story — I shouldn’t even share it. There were a couple of unknown numbers on my voice mail the other day, and it was Kamala checking in,” he said. “I am really proud of her, and I don’t say that to be patronizing.”
Ms. Harris’s aides said she had most recently called the governor to ask how California was faring after it was struck by Hurricane Hilary and an earthquake.
Mr. Newsom, who is barred from seeking a third term as governor, has assembled a skeleton structure of campaign aides, in effect a campaign-in-waiting.
He has raised $3.5 million for Democratic candidates, Mr. Biden among them. He is also distributing money from his political action committee, Campaign for Democracy, further enhancing his standing with Democrats candidates and political operatives around the country. “If he ever ran for national office, he has a record to run on,” said Sean Clegg, one of Mr. Newsom’s top advisers.
Still, should Mr. Newsom seek to expand his political ambitions, he faces some serious obstacles.
Mr. Newsom won a second term as governor in 2022 with nearly 60 percent of the vote. But he is a Democrat in an overwhelmingly Democratic state and has never had to face a tough Republican opponent.
Mr. Newsom has become the face of a state with a long history of innovation and prosperity, but that state also brings with it some of his party’s biggest challenges: homelessness, a housing crisis and what may be the end the kind of growth that has defined the California dream. California has always been a political and cultural outlier and has, more than ever, become a rallying point of the right on issues like crime.
Jessica Millan Patterson, the leader of the California Republican Party, said Mr. Newsom could prove an appealing national candidate, but that he would not play well with swing voters in many states.
“It’s a really difficult sale,” she said. “I don’t think most of the country is looking at California and saying, ‘That’s what we should be doing.”
The last California governor elected president was Ronald Reagan, a Republican; but by the time of that election, in 1980, he had been out of office for five years.
Jerry Brown, a former California governor who ran for the White House and lost three times, said that none of the hurdles Mr. Newsom faced were insurmountable. “The most important thing is the candidate and the times,” Mr. Brown said. “If the candidate fits the time, I don’t think the geography and the cultural differences matter as much.”
Mr. Newsom acknowledged all the hurdles. “It’s the surround-sound nature of the anger machine that is 24/7, wall-to-wall anti-California,” he said. “People’s entire careers are built on tearing this state down.”
But Mr. Newsom argued — while insisting he was engaging in a hypothetical discussion, since he is not running for president — that being governor of a state like California would make someone particularly qualified to run the nation.
Not that it matters, by the governor’s telling. Mr. Newsom said becoming president was “never on my list” and that he was not one of those Democrats who grew up with a photograph of John F. Kennedy on his wall, as he put it, drawing an unstated comparison to Bill Clinton and Pete Buttigieg, the transportation secretary who ran for president in 2020 and may well run again in 2028.
“Look, in 2028, 99.9999 percent of people will not remember a damn thing about what we did in this election,” he said. “They will all fall in love with whomever it is — and there will be 30 of them on the stage. No one is naïve about that.”
Michael D. Shear contributed reporting from Washington.