2014 national exit poll on 2016 candidates

[Mehmentum]

Even with the incredibly favorable electorate this year, the Republicans have hilariously horrible image problems.

[Mehmentum]

Is this not to be expected when no Republican candidate can break 15% with their own primary electorate?

No it isn't expected.

Just because a voter votes for a different candidate in the primary, it doesn't mean they think every other candidate would be a bad president.  The fact that only a quarter of a very conservative electorate thinks each Republican candidate would make a good president and practically two thirds of the electorate think they would make a bad president is a very bad sign.