In a survey last month, 47 percent said they were "scared" of Donald Trump as the Republican nominee. That's interesting, but let's put it in context. No recent Republican candidate has scored so high on the "afraid" scale in recent elections. See the graphic below.
The ANES data can be found here. And yes we're a bit apples-and-oranges in comparisons, given the nature of the ANES academic surveys versus one-shot commercial surveys, but still you get the idea. The highest percentage of people being "afraid" of the GOP candidate was 43 percent in 2004. It's my hunch that Trump will break the "afraid" record once ANES collects its 2016 data this Fall.
Oh, but how about Dems, you ask? The Dem data is here. The highest was for Barack Obama in 2012 (34 percent).
I also wonder whether Trump will break another ANES record, on the question of how "knowledgeable" you perceive the candidate to be. In this case, you'd bet he may set a low record. For GOP candidates, according to ANES data, the lowest was whether "knowledgeable" described a candidate "extremely well" was 16 percent for George W. Bush in 2000 (Gore was 25 percent). The lowest ever for a Dem since 1980 was 15 percent for Michael Dukakis in 1988. I'm betting Trump, when ANES runs its surveys, takes the record from Bush and gets around 15 percent.
From a PhDweeby perspective, we call this affect (angry, hopeful, etc.) and traits (knowledgeable, honest, etc.). Neither are terribly predictive of vote, at least not consistently across elections. You can find a whole list of them via the ANES data here, just scroll down to #7. I'm at home, otherwise I'd access the raw data and have even more fun.