They don't like any of them much (and who can blame them?)
I find this astonishing:
Among Republicans, 49 percent view Donald Trump favorably; less than half have favorable opinions of Ted Cruz or John Kasich. About a third has unfavorable opinions of Trump and Cruz, while 44 percent don't have an opinion of Kasich.
The reason that's astonishing is that none of them have a majority of Republicans who view them favorably. Has that ever happened before?
Contrast that with the Democrats who are also in the middle of a very spirited contest. (The poll I cited above hasn't released any numbers on the Democratic race so I couldn't compare exactly. The following comes from a recent Gallup poll)
Seven in 10 Democrats have a positive view of each of their party's two contenders. Clinton has a little more negative baggage, with a 26% unfavorable rating compared with Sanders' 13%. Sanders has a somewhat higher percentage responding "Never heard of/Don't have an opinion." But they are both well-liked.
That number includes Democratic leaners so most of the independents are captured.
In March 2012 ... Mitt Romney, had a 67% favorable rating at that point, much higher than either Trump's or Cruz's today. In 2008, in a March Gallup poll, John McCain came in with an 87% favorable rating from Republicans, and Obama had a 79% favorable rating from Democrats. Clinton back then had an 80% favorable rating among Democrats, a little higher than she is getting today -- but not by much.
Republicans to date are clearly more fractured and certainly less positive about the two leading candidates for their party's nomination than are Democrats. Carried forward, this means that the Republicans could have more of a challenge motivating voters in the fall. Something that could disrupt this pattern would be the entry of a current non-contender (like Paul Ryan) into the race, but this too would likely leave at least some supporters of the current candidates up in arms and upset.
*I did conflate two polls there so the comparison between the GOP and the Dems may not be fully accurate. But in general the point stands. A majority of people who vote for Democrats like both of their candidates and Republicans not so much.