Here’s a blast from the past: Bill Weld is running for president. Speaking in New Hampshire on Friday, the former Massachusetts governor announced that he was forming an exploratory committee to seek the Republican nomination for president. Weld ran for vice president in 2016 on the Libertarian Party ticket, but he’s working within the two-party system this time. That’s smart in one sense — it’s extremely hard to win as a third-party candidate in the United States — but Weld also faces steep odds in challenging the sitting president in a GOP primary.

In all likelihood, President Trump would crush any Republican who tries to primary him. An incumbent president has not lost a bid for renomination since Chester A. Arthur at the GOP convention in 1884 — meaning that it’s never happened in the modern era of presidential primaries. And Trump enjoys a higher approval rating among members of his own party even than recent presidents who cruised to renomination, like Ronald Reagan and Barack Obama. (In a recent Fox News poll, 87 percent of Republicans approved of his job performance.) And in early, hypothetical polls of the Republican presidential primary in 2020, Trump has massive leads on even well-known opponents such as Mitt Romney, though Romney has given no indication he’s considering a run. No poll so far in our database has tested Trump against the relatively unknown Weld.