Donald Trump has some big polling problems. Yes, the GOP frontrunner has blown away his opponents in many primaries and caucuses. But he also suffers from ultra-high unfavorable ratings, even among the groups that should like him.

On Thursday, he tweeted that he could bring the Republican Party together, on the same day that two different polls showed the difficulties he might still face as the campaign wears on.

A new study gives a few more signs of what ails the GOP, and could ail Trump come November. Not only do the party's voters doubt whether they can fall in line behind their frontrunner, but they are widely divided on an array of issues (and therefore candidates). And while it's true that Democrats get angry from time to time about who's more "progressive" or could better "stand up to Wall Street," new data from the Pew Research Center suggest that the problem of bringing together a big swath of diverse viewpoints is much bigger for Republicans right now.

Pew found that 64 percent of Democratic and leaning-Democratic voters believed their party would "solidly unite" behind Clinton as a nominee. That's right in line with how Republican and Democratic voters felt about McCain and Obama, respectively, in 2008.

For Trump, the figure is only 38 percent. Fewer than 4 in 10 GOP and GOP-leaning voters believe their party will unite behind the candidate with a massive delegate lead.

It's possible there's a perception problem there — maybe those voters underestimate their fellow Republicans' (and Republican-leaners') willingness to back Trump. But other Pew data show just how big of a gulf a GOP candidate will have to close.

The data also make clear just how much bigger it is among Republican candidates' supporters than Democrats'.

The average gap between the two farthest-separated views on any given topic on the Republican side is 20.6 points. The average window between Sanders' and Clinton's supporters views, meanwhile, is about 7.8 points.

The only topics in Pew's list that seem to really separate Sanders and Clinton supporters are foreign affairs (whether U.S. global involvement makes things better or worse) and to what degree the economic system favors powerful interests.

Meanwhile, Republican candidates' supporters are widely divided on a variety of topics — immigration, anger with the government, "scrutiny" of Muslim Americans, trade, and abortion.

This isn't to say the GOP can't unify in November. For one thing, people choose to vote — or not vote — for a candidate based on a lot of other, hard-to-pin-down factors (think how "presidential" someone is or the perennial "would you have a beer with her/him" question).

Ted Cruz and John Kasich's supporters, for example, clearly have some sizable divides on topics like how much scrutiny Muslims should be subject to, as well as immigration and abortion. But only around 25 percent of Kasich's supporters say Cruz would be a "poor" or "terrible" president. And only 17 percent of Cruz's supporters say so of Kasich.

And then there is Trump. Fifty percent of Cruz's supporters and 55 percent of Kasich's say Trump would be "poor" or "terrible."

It's not just among Republicans. Trump is also by far the least confidence-inspiring general-election candidate, by Pew's data. Fifty-nine percent of Pew's registered-voter respondents said he'd be a "poor" or "terrible" president.

The Pew data suggests a counterintuitive problem for the GOP: that its candidates' general- and primary-election standings are upside-down right now. Kasich, the GOP candidate who seems to be at least somewhat acceptable to many potential general-election voters (at least per this data) is also doing by far the worst in primaries and many polls. And Trump, who is by far on the clearest path to the nomination, also is so polarizing that it could cripple his general election chances.

Pew isn't by any means the only organization to have found these sorts of problems for trump. An ABC Washington Post poll released Thursday found Trump was viewed unfavorably among more than 50 percent within even Republican-leaning demographics like white men, white self-described evangelicals, non-college-educated whites, and conservatives.

But there's another conundrum here: Kasich and Cruz, many of whose supporters seem to say they could stand the other candidate, clearly haven't inspired the fervor (read: the huge vote totals) that Trump has. So even if they could be more acceptable in a general election, the question is if they could drive turnout.

That is, how many would people leave the house to vote for someone they think would be an "average" president? Thirty-nine percent of Pew's registered-voter respondents said that of Kasich, the most of any of the five candidates.

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