I actually know people who voted for McCain and told me it's because of the poll that showed he was the only candidate that could beat Hillary, I think that poll was 9 months before the election.
Pardon me while I go laugh at your silliness.......
Historic Whispers: Ronald Reagan Had Little Chance of Winning the Primary
White House political strategists have concluded—regretfully—that Ronald Reagan is fading and will have little chance of winning the Republican presidential nomination in 1980. Why the regrets? Because Carter's aides are convinced that the conservative, 68-year-old former California governor is an easy target. (April 2, 1979)
Here's another blast from the past, March 10, 1980. The GOP establishment had decided they needed another candidate besides Bush to stop Reagan and started recruiting Gerald Ford:
ABC News - Harris poll: FORD LEADS BOTH CARTER AND REAGAN, ALTHOUGH STILL UNDECLARED CANDIDATE
"Former President Gerald Ford is the first choice of Republican and independent voters to head the GOP ticket, even though he has not yet declared himself a candidate for the Republican nomination.
Ford also leads President Carter among the general electorate."
Harris Poll January 29, 1980:
CARTER NOW FAR AHEAD OF BOTH REAGAN AND BUSH
"President Carter so dominates the American political scene now that his margin over Ronald Reagan in a post-Iowa trial heat has risen to an overwhelming 65-31 percent."
Also, Time magazine ran a big story in March of that year basically saying Reagan was unelectable. Gallup had a poll in that time frame with Reagan down 25 points.