“Could Donald Trump be, um, primaried?” That’s the whispered question I hear more often than you might think from plenty of exhausted Republican elected officials, particularly after a long week of dodging reporters looking for comment on the president’s latest antics. “I mean, he’s just killing us!” they say, before hustling away to safety.

Could the president be beaten in a primary? The short and easy CW is, lots of luck! Only two incumbent presidents have faced serious primary opposition in the past 50 years: Ronald Reagan challenged Gerald Ford in 1976, and Ted Kennedy took on Jimmy Carter in 1980. Both lost after spirited contests. Two others faced less serious opposition; George H.W. Bush dispatched Pat Buchanan in 1992, and Richard Nixon crushed the two Republican congressmen — one from the left and the other from the right — who challenged him in 1972. The sole president in memory knocked out of office by the primary process was Lyndon Johnson, who abandoned his reelection campaign after Minnesota Senator Eugene McCarthy stunned observers by finishing a close second — 7 points behind LBJ — in the New Hampshire primary.

Could such an early state stumble happen again? (I suspect Ohio Governor John Kasich is particularly curious, having run second to Trump in 2016’s contest in New Hampshire). Doubtful. While such a sign of political weakness might once have driven an honor-bound president to resign, shame is a nonfactor to Trump. To defeat him, you would have to actually win early and often in the primary states and assemble a majority of convention delegates. That’s the simplest way and the hardest.