Of the March 15 primary states, the only state in which the results looked a bit… odd is North Carolina. Democratic primary turnout was super-high, nearly as high as Republican, Trump did not, as in Florida, get nearly the same number of votes as Clinton, but, rather, far less, and Bernie Sanders got an unusually high percentage of the primary vote for a Black Belt state.
Turns out, in North Carolina, there were 2,052,250 registered Republicans and 2,270,395 Romney general election votes, a ratio of 1.1 Romney votes per registered Republican. There were 2,870,693 registered Democrats and a mere 2,178,391 Obama votes, a ratio of .7588 Obama votes per registered Democrat. Democrats simply have a very lopsided party registration advantage there, and it is well known that DINOs tended to vote against Hillary Clinton, but not against Bernie Sanders.
In Florida, where the results were more normal-seeming, there were 4,581,056 registered Dems and 4,237,756 Obama votes, a ratio of .925 Obama votes per registered Democrat. Meanwhile, there were 4,163,447 Florida Romney voters and 4,137,890 registered Republicans, a ratio of 1.01 Romney votes per registered Republican. So the partisan turnout gap in Florida isn’t nearly 35 points, as it is in North Carolina, but less than 8 points, thus explaining Trump’s competitive position against Clinton in the Florida primary.
Doing two-party vote shares and registration percentages by county would be a tad time-consuming, so I’m not going to bother with it. It’d be interesting, though.