One of the giant caveats floating around next to Donald Trump's 2016 candidacy has been that, despite his decent standing in a splintered field, he was viewed so negatively by Republican voters that it was hard to see how he could actually build on his base of support.

Well, guess what.

When Monmouth University polled Republican voters in June, Trump barely registered, showing up at 2 percent in the polls and with favorability ratings that were far under water; 20 percent of voters viewed him positively and 55 percent viewed him negatively. That gave him a net negative-35 favorability -- by far the worst in the field. But, again, he was polling at 2 percent.

In Monmouth's new poll, he's jumped to 13 percent in the crowded field -- by far the biggest improvement. (Anyone below that diagonal line is doing worse. Anyone above, doing better -- and the further from the line, the bigger the improvement.)

In part, that's because way more people view Trump favorably now. He's now seen positively by 40 percent of Republicans, compared to 41 percent who view him negatively. Most of the Republican candidates still have higher net favorable ratings than Trump, yes, but no one has seen any jump like his.

The closest is Jeb Bush, who went from plus-5 to plus-20 -- a good reminder that some of Trump's gain is due to his having at last announced his candidacy.

But not all of it. Notice Chris Christie, down there at the bottom, viewed more unfavorably than any other candidate, despite also having made a recent campaign announcement. Part of Trump's leap in the polls is certainly his having stumbled onto a popular issue -- one that drives the Republican establishment batty.

Once upon a time, Trump was too unpopular to make it very far in the race. He's still unpopular, and this is only one poll, so we'll have to say if others confirm it. But it seems fair to say that ruling him out based on his unpopularity might no longer apply. He's not popular in the GOP, but he's no longer a pariah.