Rush Limbaugh, the relentlessly provocative voice of conservative America who dominated talk radio for more than three decades with shooting-gallery attacks on liberals, Democrats, feminists, environmentalists and other moving targets, died on Wednesday. He was 70.

His wife, Kathryn, announced the death at the beginning of Mr. Limbaugh’s radio show.

“I know that I am most certainly not the Limbaugh that you tuned in to listen to today,” she said before adding that Mr. Limbaugh had died of lung cancer that morning.

He had announced on his show last February that he had advanced lung cancer. A day later, President Donald J. Trump awarded him the Presidential Medal of Freedom, the nation’s highest civilian honor, during the State of the Union address.

Mr. Limbaugh soon resumed his broadcasts, and his adoration for Mr. Trump. As the Covid-19 pandemic swept the nation, he likened the coronavirus to the common cold. And in October, as Election Day neared and Mr. Trump recuperated from the virus himself, he joined Mr. Limbaugh on the air for a two-hour “virtual rally,” largely devoted to his grievances.

“We love you,” Mr. Limbaugh assured the president on behalf of his listeners. But 10 days later, Mr. Limbaugh told his audience that his cancer had grown worse and, despite treatments, was “going in the wrong direction.”

Mr. Limbaugh had been a divisive darling of the right since launching his nationally syndicated program during the presidency of his first hero, Ronald Reagan. Using often misogynistic and racist language and trafficking in conspiracy theories, he pushed conservative talk radio into extreme right-wing territory while building a regular audience of as many as 15 million Americans.

That following, and his drumbeat criticisms of President Barack Obama for eight years, when the Republicans were often seen as rudderless, appeared to elevate him, at least for a time, to de facto leadership among conservative Republicans.

Such talk became obsolete in 2016 with the meteoric rise of Mr. Trump, who, after several flirtations with presidential races that were never taken very seriously, suddenly burst like a supernova on the national political landscape. Mr. Trump became president and Mr. Limbaugh, off the hook, became an ardent supporter.

“This is great,” Mr. Limbaugh, sounding positively giddy, said of his new champion in the White House. “Can we agree that Donald Trump is probably enjoying this more than anybody wants to admit or that anybody knows?”