Hard to understate Rush Limbaugh's influence, because he lasted so long. In 1994, Republicans who won Congress felt he'd helped so much they made him an honorary member. 26 years later, as Trump tried to overturn an election, Limbaugh was still on the air, talking of secession.
Whenever I have reported in a new place, one way I try to get the feel of it is by listening to talk radio as I drive. In many rural communities the big midday program was not anything local. It was Rush, hour after hour, three hours a day.
Needless to say, the show was a stew of hyperbole, partisanship and disinformation, with ads offering help with tax problems or addiction. But there was nothing quite like it. He'd come on with no guest, just a newspaper article. He'd read it to his audience and talk for an hour.
Limbaugh was an extraordinary talent, and had he been more of a good-faith actor--never mind the partisan leaning, just more responsible--he might have had a different influence. But that he had a huge political influence is impossible to deny.