He says he wants to stop the president from being re-elected. There’s no better way to do it.

Gage Skidmore/Wikimedia Commons

No one can ever truly know what motivates someone to run for president, but to hear newly minted Democratic candidate Mike Bloomberg make the case, his prime objective is to stop Donald Trump from being re-elected.

“If President Trump wins another term in office, we may never recover from the damage that he can do,” the former New York mayor and media billionaire said during his November 25 announcement. “The stakes could not be higher. We must win this election.” Trump, he went on, is “an existential threat to our country.”

Bloomberg’s tens of millions already spent in support of Democratic congressional candidates and on gun control and clean energy advocacy were already enough to prove his sincerity about stopping a right-wing agenda. The more than $100 million that he’s committed to spending on staffing and advertising for his campaign is proof that he’s taking his latest project seriously as well.

On Saturday, Bloomberg said that he had entered the Democratic primary because he no longer believed that any of the other candidates could defeat Trump. His advisers have also repeatedly told journalists that Bloomberg isn’t in the race to stop the more liberal candidates from winning but rather because he believes his rivals are unable to oust the incumbent.

While there’s no doubt that the Democratic field has its weaknesses and that Bloomberg’s millions are likely to help him garner significant name recognition and an audience for his policy ideas, his chances of actually winning the nomination are modest at best. He is, if anything, a less dynamic and “likeable” public speaker than the other leading charisma-challenged candidates. His controversial record on “stop and frisk” policing policies that targeted black and Hispanic men for governmental harassment means he will have great difficulty attaining the support of African American voters. And his refusal to divest himself of his billion-dollar news organization, even as it’s vowed to never investigate him, will dog him throughout the primaries.

But if he truly does believe that defeating Trump is what matters most, Bloomberg could play a vital role by running for president not as a Democrat, but as a Republican—the party affiliation he had as mayor of New York City.

Recent history suggests that incumbent presidents who face strong primary challenges are severely weakened by them. George H.W. Bush was unable to recover GOP loyalty after being damaged by Pat Buchanan in 1992. Jimmy Carter was wounded by Ted Kennedy’s 1980 challenge. And Ronald Reagan’s 1976 challenge to Gerald Ford left the latter severely damaged. In all three cases, the president who faced a primary lost the general election.

While Trump retains strong support among Republicans, some polls suggest that this loyalty is only due to the fact that many GOP voters are more motivated by opposition to Democrats than loyalty to him. In a June survey by HarrisX, 44 percent of registered Republican voters said they wanted Trump to face a primary challenge—significantly more than the 33 percent of Democrats who wanted Barack Obama to face a primary challenge in 2012, according to a 2011 Pew Research Center poll.

The HarrisX finding was similar to May research conducted by SurveyMonkey, which found that 42 percent of conservative-leaning respondents were open to the idea of backing a Trump challenger. Fourteen percent of Republicans said they would “absolutely” back an intra-party contender.

Trump already has two Republican rivals, former Massachusetts Governor Bill Weld and former congressman turned conservative pundit Joe Walsh. But the strong support that the president receives from white evangelicals and the right-wing media has ensured that neither man will likely to be able to raise enough money to mount a credible challenge to Trump. Even worse, a number of Republican state party organizations are protecting Trump by abolishing their state’s 2018 presidential primary elections.

But Bloomberg’s millions of dollars could easily put a harsh spotlight on Republican attempts to silence dissent within their caucus. The fact that Bloomberg ran twice on the Republican platform would be an advantage to him in this regard. At the same time, several of his expressed views—opposition to single-payer health care, skepticism about the MeToo movement, defense of Wall Street—would become an advantage to him, rather than the negative that it is among progressives. While GOP gun control opponents will surely object to Bloomberg in the race, average Republican voters are not nearly as fanatical about firearms as their political leaders.

Bloomberg’s policy and financial background also make him the perfect GOP foil for Trump. His fortune is much larger and actually built from scratch—unlike Trump’s. What’s more, Bloomberg’s policy accomplishments as New York mayor, such as driving its poverty rate down, are more substantive than Trump’s as president. The famously peevish former reality television show host will be unable to contain his ire as Bloomberg and others repeatedly show the contrast. No other potential intra-party rival could possibly irritate Trump as much as Bloomberg can.

But most importantly, a Bloomberg insurgency within the Republican Party could help resuscitate the moribund moderate wing of the GOP—a project that would contribute greatly to America’s political system for decades.

Simply put, Mike Bloomberg won’t be able to win the Democratic nomination. If he wants to spend his money wisely, he should focus on mortally wounding Donald Trump. The best way for him to do that is to challenge the president as a Republican.