Donald Trump is the most vulnerable incumbent president in decades. Struggling with a stubbornly low approval rating, plagued by scandal and facing a raft of criminal and civil investigations, he threatens to take his party down to an epic defeat if he's renominated. You'd think Republicans might be open to an alternative.
But you can't beat somebody with nobody, and practically speaking, nobody is the present alternative. So far, Trump has only one GOP challenger, former Massachusetts Gov. William Weld. Maryland Gov. Larry Hogan is publicly pondering a race. Former Ohio Gov. John Kasich is also a possible entrant.
None of them is likely to pose much danger to Trump. All come from the moderate wing of the party, which is not so much a wing as a handful of feathers. They might appeal to many independents and even some Democrats. But Republicans are not going to abandon a president who has relentlessly catered to conservatives on taxes, abortion, immigration, judges and Iran.
The history of serious challenges to incumbent presidents is that they don't arise from the middle of the spectrum. They spring from the left in the Democratic Party and the right in the Republican Party. The rebels could claim to speak for the hardcore faithful, not the soothing centrists.
In 1992, it was Pat Buchanan who mounted a mutiny. He vilified George H.W. Bush for breaking his promise not to raise taxes, and he railed against gay rights, abortion, free trade and immigrants. He got nearly 38 percent of the vote in the New Hampshire primary.
In 1980, President Jimmy Carter, dogged by high inflation and gas lines, had to contend with Sen. Ted Kennedy, whose family embodied modern liberalism. Kennedy won a dozen contests in the Democratic campaign.
The most successful challenge, however, came in 1968, when Eugene McCarthy, vocally opposing the Vietnam War, stunned President Lyndon Johnson by getting 42 percent of the vote in New Hampshire. Johnson soon excused himself.
Those examples illustrate why Trump is not going to fall to a Weld or a Kasich. If anyone is going to bring him down in the Republican primaries, it will be someone with powerful appeal to the base voters, who have stuck with Trump so far.
Who would that be? The most plausible candidate is his former U.N. ambassador, Nikki Haley. She is assumed to be looking to a 2024 presidential bid.
But if she is not primed to jump in if and when Trump suffers a major setback, she is missing what could be the chance of a lifetime.
Her assets are hard to overstate. She's an uncompromising Reaganite who thrilled hawks with her aggressive rhetoric at the U.N. Critical of Trump in the primaries, she was a loyal soldier after he won. She somehow managed to stay in his good graces and depart the administration with her reputation intact, a feat akin to staying dry while swimming in a rainstorm.
She has not been so rash as to challenge any important article of right-wing dogma. As governor of South Carolina, Haley got a 100 percent rating from the National Rifle Association, won the endorsement of the anti-tax Club for Growth PAC and got a score of zero from NARAL Pro-Choice America.
Compared with Trump, she is more closely aligned with congressional Republicans on policy toward Russia, NATO and Saudi Arabia. If she were to run against him, she would draw on a large stock of conservative goodwill.
Could she win? Given today's conditions, no. But conditions are likely to get worse for Trump, not better. Republicans would be strongly reluctant to abandon him — unless he looked like a sure loser and they had an alluring alternative at hand. Haley would be exactly that.
She might be the candidate Democrats would least like to run against. She would be more than capable of uniting the GOP. But as a first-generation Indian-American woman who removed the Confederate flag from the South Carolina Statehouse grounds, she would also be relatively well-positioned to appeal to some independents who find Trump distasteful, if not repulsive.
Haley would help negate the party's well-deserved reputation for shortchanging women, minorities and immigrants. Her sunny mien and sense of humor evoke Ronald Reagan — and contrast with Trump's inexhaustible rancor.
Trump may figure that the Republican electorate will stick with him no matter what, and he may be right. But with the right timing, Haley could put that loyalty to a real test.
Steve Chapman blogs at http://www.chicagotribune.com/news/opinion/chapman. Follow him on Twitter @SteveChapman13 or at https://www.facebook.com/stevechapman13. To find out more about Steve Chapman and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.