Well, it comes out if he's the one running as a Republican. If he's not, just use his rhetoric to hurt the republican who is running.
"Donnie talks a good game, but let's look at his record:"
or
"You know, I disagree with just about everything Donald Trump says, but I do agree with him that cutting social security and medicare like my opponent wants to do is dumb."
Well, it comes out if he's the one running as a Republican. If he's not, just use his rhetoric to hurt the republican who is running.
"Donnie talks a good game, but let's look at his record:"
or
"You know, I disagree with just about everything Donald Trump says, but I do agree with him that cutting social security and medicare like my opponent wants to do is dumb."