What the presidential and mid-term elections showed us is that people liked DumBama, but they hated his policies. They wanted him as President, but they didn't want him in charge.
No, what the midterms show is that a lot of people have kind of given up. The 2014 midterms had the lowest voter turnout since 1942, and they can't excuse a draft for that.
So the winnner in 2014 was... apathy. You won a lot of elections people didn't really understand, by less votes th an you got in 2012.
Point- not one winner in a Contested Senate Race in 2014 got more votes than Mitt Romney had gotten 2 years earlier.
So you've really changed no minds.
Now, that said, yes, I think a Charismatic GOP candidate could beat Hillary if he can win over women and minorities. Fiorona might win over women, but she probably won't survive much longer when Republican rand and file types figure out she's pro-choice and pro-marriage equality.
Rubio might win over Hispanics if you can ignore his general gutlessness on his own immigration bill.
But more than likely, the GOP will just nominate Bush and people might actually remember how badly the Bush Crime Family messes things up when they are in office.