It would have been one of the biggest blowouts of all time. Southern Democrats would all have abandoned the McCarthy ticket and would openly be backing Wallace. Many, many Northern Democrats would be jettisoning the Democrats and endorsing Rockefeller. Indeed, if there were such a matchup, I believe that Nelson Rockefeller would have become the only Republican in history to win the endorsement of the AFL-CIO.
People who think McGovern was a poor candidate would have been appalled as to just how bad a candidate Eugene McCarthy would have been. I spent my freshmen year at a college where Eugene McCarthy had been a professor the a year or two before I arrived there. Several of the professors I had knew him and each one indicated that the man was incredibly naive. He would ramble on about poetry, but he was very much an ego-driven idealist who could not help but alienate people he would need to achieve his stated goals.
The Goldwater conservative movement would have supported Rockefeller because of how bad a McCarthy Administration would have been, but there would have been all sorts of backbiting and scheming for control of the party behind the scenes. Nelson Rockefeller did, however, understand politics, and he'd have made every alliance and accomodation with conservatives in order to win the election.
The question here would be who the running mates would be. Here is a guess:
Gov. Nelson Rockefeller (R-NY) / Gov. James Rhodes (R-OH)
Sen. Eugene A. McCarthy (D-MN) / Sen. Wayne Morse (D-OR)
Gov. George C. Wallace (D-AL) / Rep. Walter Baring (D-NV)
In this case, it's likely that many Southern states would have named the Wallace ticket as the Democratic ticket as the Dixiecrats did.
