That is an utterly ridiculous position to hold.
Neither Romney or Trump are conservative, but at least Romney is somewhat beholden to a right of center voting block. Romney will at least have to throw the occasional bone to conservatives such as court nominations, cabinet positions, undersecretary's, etc. Trump as a 3rd party candidate would not be beholden to conservatives at all. He would not govern as a conservative, and would not have to care what conservatives think.
Romney is not himself conservative, but is politically schooled enough to at least understand how to pretend to be one. Trump wouldn't know conservatism if it beat him upside the head. With Trump, you could easily see he didn't understand conservatism by the way he played to a caricature of what he thought the majority of conservatives wanted when he was pretending to toy with a primary run.
Romney is a RINO. Trump is an absolute clown.
Romney is a lying snake who I will not vote for after the way he and his campaign smeared Newt and all his competition out of the race. He couldn’t stand on his liberal record so he destroyed his competiion instead. I WILL NOT vote for Romney. Now I have conservative pundits trying to tell me that Romneycare is conservative and that Romney is conservative. They are moving conservatism left so the label fits their chosen one and it makes me sick.