Reagan won two landslide elections and there was a conservative movement before anyone had heard of Rush Limbaugh. There were maybe three major conservative media figures most Americans had heard of or seen on television in 1980 (George Will, William F. Buckley, Jr. and Jack Kilpatrick from Agronsky & Co.).
Rush may change some people's minds by his confidence or humor, probably turning off or offending others (mostly liberals, feminists or some moderates). Lightning rod. Activist liberals spend more time obsessing, agitating and worrying about it primarily because of the kind of anti-liberal jokes Limbaugh tells, complete with voice impressions and Shanklin's songs (similar to SNL). Since they are not used to being made fun of and satirized (they get free passes mostly from the MSM), it's a shock and they are a bit outraged. It goes back to his voice impression of Jesse Jackson and his definition of feminism as a way "unattractive women get access" to attention and the mainstream of American society. So he has agitated liberal feminists and African Americans.
But the image of Rush as the mastermind boogieman of the Right, which liberals use in these anti-Rush panics, is overblown and exaggerated. They just can't stand it that someone with his views is that popular and successful. It's about silencing dissent and opposition. Deep down they probably also know that it's funny.
The Shanklin parody of ELO's "Don't Bring Me Down" about Obama crashing the stock market that Limbaugh plays is a riot.
That's what happened, partly, in 2008. Mostly it was because That One was perceived as 'cool', compare to the 'old man', and white voters were anxious to prove that they weren't racists, and would vote for a black candidate.
Jay Cost, Rush Pays.