Ginsberg explained that 73 percent of the delegates at the GOP convention “are chosen at state conventions or by state party executive committees with little or no input from the candidate who wins that state.” Those delegates are bound, on the convention’s first ballot, to vote for the presidential candidate chosen by their state’s voters. But they’re not bound to do so on subsequent ballots. And even on the first ballot, they’re not bound to vote in the candidate’s interest on rules issues, credentials challenges, or other questions that can loom large in the arcane proceedings of the convention.

“So if you were to devise a plan to stop a runaway nominee,” Ginsberg said, “you would have to do a lot of state-by-state organizing, win the delegates at the convention.”

NBC’s Chuck Todd noted that Ginsberg’s plan wasn’t designed to win the nomination for any one candidate — just to keep Trump from getting it. “This is a two-week sprint to deny Trump delegates,” Todd said to Ginsberg. “This is no longer about trying to beat Trump, it’s just simply to deny Trump a majority of delegates at the convention. This is where we’re at tonight.”