Are the Republicans who are unhappy with Trump as unhappy as previous members were with Dole, McCain and Romney?

Dole and McCain were "next in line" candidates. Romney was the new establishment RINO they thought could beat Obama at his own game, being squishy and soft. You can't out squish Obama. Romney proved he could not beat an eminently beatable incumbent.

The GOP helped create the circumstance for Trump to make the scene and be successful at pulling away primary voters. Remember, Jeb was the heir apparent. He had all the money, all of the support, he was coming on strong for a Bush - Clinton redux. At least the GOP voters were smart enough to toss Jeb aside. The dems love them some Clinton. It appears they cannot get enough of sex scandals, lying, criminal activity etc. a bit like Soap Opera mongers.

I certainly have a stronger distaste for Trump than did Romney or McCain. I was unable to talk a few of my friends into voteing for McCain in the 08 election. However after 4 years of Obama, we held our noses and voted for Romney. At this point, I foresee many of us staying home again.

When we talk about the spread of the candidates across the spectrum, it's reflective of a Party in which many individual members don't really know what they want. That's because they want something that is impossible to create. They gravitate to the closest one and then go into gridlock if pushed towards another. The illogic is "I've moved more than enough for this candidate and I'm not moving an inch farther." They then blind themselves further by refusing to consider the unelectability of their candidate. The interesting thing this cycle is how the Trump people are so much in the tank for Trump. Haven't seen that fervor in a long time. So we've seen the term RINO around for some time. It's an indication of broadening of the conservative viewpoint. Things shift over time. A Blue Dog Democrat would be a middle of the road Republican 50 years ago. The party has increasing numbers shifting so far right, they really aren't Republicans anymore when you look at more traditional tenets of the party. Same thing with the Democrats pulling ever more left. That's why the largest growth block are the Independents who just won't go that far left or right.