This morning, I highlighted a key finding from the new Wall Street Journal/NBC News poll. It showed the Marco Rubio led the entire GOP field when it comes to being a guy Republican voters could see themselves supporting.

What I didn't mention: Just three months ago, that guy was Jeb Bush. But while in December, 63 percent of Republican voters said they could see themselves backing Bush, today it's just 49 percent.

And it's hardly the only poll in which Bush has seen his fortunes declining. The head-to-head polls that showed Bush as a frontrunner when he first got in suddenly show him running much closer to the field and even behind the lesser-known Scott Walker. Polls in Iowa and New Hampshire, meanwhile, also show significant swaths of the GOP can't see themselves voting for Bush.

So what has Bush done to deserve his decline in the polls? It's hard to say. His decision to dip his toe into the 2016 race has undoubtedly cast something of a spotlight on his support for Common Core education standards and comprehensive immigration reform-- two things that are anathema to much of the GOP base. Other than this, though, Bush's early performances on the campaign trail have largely gone pretty smoothly. He has openly and confidently engaged with the press and largely earned plaudits for it.

And it's hard to say it's the Bush name; after all, he's even less popular than his brother these days, according to some polls (including this one).

But the Wall Street Journal/NBC poll shows us something else that could explain it. While the vast majority of Democrats say they can see themselves backing Hillary Clinton, the 56 percent who say they could back Rubio is the highest number that anyone in the Republican field gets. And it's not just that the GOP candidates are less well known. Many Republicans simply can't see themselves backing many of the hopefuls -- including 26 percent who say this of Rubio and 42 percent who say this of Bush.

This says a lot about the GOP today. Say what you want about how good the field of candidates is; the fact that so many of the candidates are off the radar for many voters is as much about the voters as it is about the candidates. Republican voters these days are much more contrarian -- much quicker to find flaws with their candidates.

Bush did a smart thing by jumping in the race early and forcing out Mitt Romney. But in today's Republican Party, being the early frontrunner might not be the best position.