For the past two and a half months, Donald Trump has received around 25 to 30 percent support in national polls of Republicans. That's an impressive result in the 15-candidate GOP field, but it's still far short of a majority — so some have assumed that once the other candidates start dropping out, an establishment politician like Jeb Bush or Marco Rubio would be able to lock up the non-Trump vote.

But a recent poll from the Economist/YouGov, flagged by Liam Donovan on Twitter, suggests that might not necessarily be true. In a head-to-head matchup of just Jeb Bush versus Donald Trump, the poll finds Bush losing overwhelmingly — 59 percentage points to 41. Meanwhile, in a Marco Rubio versus Trump matchup, Rubio wins — albeit by the closer margin of 53 to 47.

This is just the latest indication that, as Zack Beauchamp argued last month, it's Rubio and not Bush who's the GOP's most viable Trump slayer. The Florida senator is a fresh face, better liked, and doesn't have the Bush family baggage. Rubio's image isn't set in stone — I'm particularly curious whether he can weather attacks on his past support for immigration reform — but it looks like he's a much more appealing candidate than Bush. Indeed, when Rubio and Bush are pitted against each other head-to-head, Rubio wins by an astonishing 38 point margin.

Yet there's been very little establishment coordination behind Rubio so far. A mere six members of the US House of Representatives have endorsed him, and zero sitting governors or senators have, according to FiveThirtyEight's tracker. Bush isn't doing that great in endorsements either, but many GOP insiders have deep ties to the Bush family that may make it difficult for them to back one of his rivals. Meanwhile, Rubio is much newer to the national scene, and hasn't built comparable connections among the establishment.

So this could prove an important test of whether party elites can successfully coordinate behind the candidate who has the best chance of stopping a candidate they hate. If evidence keeps piling up showing that Rubio is a stronger candidate than Bush, the establishment should theoretically swing behind Rubio in order to stop Trump. Yet GOP insiders funneled more than $100 million to Jeb Bush's campaign and its allied Super PAC in the first half of the year — cash that Bush's team can use on a whole lot of negative ads. That means that unless Bush selflessly chooses to quit the race, as Matt Yglesias suggested a few weeks back, it could be quite messy and difficult for elites trying to show him the door.