One of the strongest candidates for US president in 2024 may be one who’s not yet in the race. There’s growing evidence that Gavin Newsom, the charismatic and energetic Democratic governor of California, is running something of a shadow campaign to Joe Biden and ready to step up if, or when, the incumbent is out of the running. Several developments in recent days suggest Newsom, who romped to re-election a year ago without really campaigning, is ready to bring forward what was already expected to be a strong run for the presidency in 2028. There are mounting concerns inside the Democratic party, matching polling among voters, that Biden is too old for a second term, the start of which in January 2025 would see him two months past his 82nd birthday if re-elected. Some want him to stand down. Newsom, 56, is among a generation of younger, prominent and popular Democrats expected to emerge from the shadow of the old guard, and has stolen a march on his peers with a series of bold moves many analysts see as strategic. Even movie star Arnold Schwarzenegger, himself a Republican former two-term governor of California, thinks a Newsom run at the White House is inevitable. “I think it’s a no-brainer. Every governor from a big state wants to take that shot,” Schwarzenegger said earlier this year. But not all Democrats appear thrilled at the prospect. Pennsylvania US senator John Fetterman, at a dinner in Iowa, connected Newsom with Dean Philips, a congressman who said he is challenging Biden. “[There are two] running for president right now,” he said. “One is a congressman from Minnesota, the other is the governor of California, but only one has the guts to announce it.” This week, Newsom made a financial donation to a Democratic mayoral candidate in Charleston, South Carolina, 2,800 miles from his governor’s mansion in Sacramento. Reaching into political elections in other states is, experts say, a sure sign of a potential presidential candidate wishing to raise their profile on the national stage. “South Carolina is an early state in the primary process for Democrats, and doing well in the early states is seen as momentum for later ones,” said Eric Schickler, professor of political science at University of California, Berkeley, and co-director of its institute of governmental studies. “In fact, Biden’s win in South Carolina is really what propelled him to the top 2020, so building connections to important politicians in the state can certainly be seen by potential candidates as an important step.” Newsom has publicly denied that he has sights on Biden’s job. “I’m rooting for our president and I have great confidence in his leadership,” he told Fox News earlier this year. But while Schickler believes Newsom’s own thinking about the timing of any White House run probably hasn’t changed, he says circumstances have. “The Democratic party’s nervousness about Biden has certainly increased, and with him polling behind Donald Trump in many states, his low approval ratings, young voters being especially disenchanted with Biden, all of that has heightened interest among a lot of party supporters in an alternative,” he said. That alternative might not be Kamala Harris, who as vice-president would usually be assumed Biden’s heir apparent. Her public approval is currently as low as the president’s. So a rising, often progressive-leaning politician such as Newsom, with a wealth of executive and legislative experience, and a willingness to counter head-on Republican policies and personalities, makes for an attractive proposition. “It’s not a situation where there’s like 20, or 50, or 100 Democratic leaders who could be viewed as legitimate. If there were such a group, Newsom has positioned himself pretty well and would be on a very short list along with [Michigan governor] Gretchen Whitmer and a couple others,” Schickler said. “The problem is the party. There’s just a lot of different voices, a lot of different constituencies, and not really anybody or any group that could authoritatively say, ‘Oh, it’s Newsom’. “[But] he would certainly be one of the most serious people. The things he’s doing now, it helps him for 2028, which still is the most likely scenario, and certainly doesn’t eliminate him if something crazy or unexpected were to happen in the next six months.” Other not so subtle clues that Newsom has sights on higher office include his $10m (£8.2m) investment earlier this year in a new political action committee designed to spread the Democratic party’s message in Republican-held states he said have “authoritarian leaders directly attacking our freedoms”. Among the targets is Ron DeSantis, the hard-right Florida governor and faltering candidate for the 2024 Republican presidential nomination. The pair will debate each other on 30 November in a highly anticipated nationally televised event once billed as a clash of two leading White House contenders. “The idea of debating DeSantis was probably a lot more appealing when it really did look like he might actually defeat Trump. In that scenario, showing you can debate him and score a lot of points helps Newsom’s visibility with the party and makes his case that he would be an effective candidate,” Shickler said. “With DeSantis not doing so well, the upside for Newson is less, but there are still Democrats who would be happy to see him debate and defeat him. He only stands to benefit, it’s just the benefit will be smaller.”