As compared to the other examples that we’ve looked at, there’s an awful lot of red in that chart — meaning, candidates whom the public views more unfavorably than favorably. Two exceptions are Mike Huckabee and Mitt Romney, who are slightly into positive territory. On the other hand, Sarah Palin and Newt Gingrich have especially poor ratings.

Several other candidates, like Mr. Thune and Mr. Pawlenty, are not yet terribly well-known — which means that they have plenty of room to grow. Nevertheless, their numbers were worse than someone like John Kerry, who was also not all that well-known, but who elicited favorable (rather than ambivalent) reactions from those voters that did know him.

So it does look like Republicans have some legitimate reason to worry. In the previous five competitive primaries — excluding 2004 for the Republicans, when Mr. Bush won re-nomination uncontested — each party had at least two candidates whose net favorability ratings were in the positive double digits, meaning that their favorables bettered their unfavorables by at least 10 points. All five times, also, the nominee came from among one of the candidates in this group. Republicans have no such candidates at this point in time.