NEW YORK — Roger Ailes, the communications maestro who transformed television news and America’s political conversation by creating and ruling Fox News Channel for two decades before being ousted last year for alleged sexual harassment, died Thursday, according to his wife, Elizabeth. He was 77.

Mr. Ailes died after a fall at his Palm Beach, Fla., home on May 10 caused bleeding on the brain, the Palm Beach County Medical Examiner’s Office said. He fell in his bathroom and hit his head.

A former GOP operative to candidates including Richard Nixon, Ronald Reagan, and George H.W. Bush and a one-time adviser to President Trump, Mr. Ailes displayed a mastery of modern messaging early in his career. Then he changed the face of 24-hour news when, in 1996, he accepted a challenge from media titan Rupert Murdoch to build a news network from scratch to compete with CNN and other TV outlets they deemed left-leaning.

That October, Mr. Ailes flipped the switch on Fox News Channel, which within a few years became the audience leader in cable news. Mr. Ailes branded the network ‘‘Fair and Balanced’’ and declared he had left the political world behind, but conservative viewers found a home and lifted prime-time commentators Bill O’Reilly and Sean Hannity to the top of the news ratings.

‘‘He has dramatically and forever changed the political and the media landscape singlehandedly for the better,’’ Hannity tweeted Thursday.

Fox News and 21st Century Fox executive chairman Rupert Murdoch called Mr. Ailes ‘‘a brilliant broadcaster [who] played a huge role in shaping America’s media over the last thirty years’’ in a statement.

‘‘He will be remembered by the many people on both sides of the camera that he discovered, nurtured, and promoted,’’ Murdoch said. ‘‘Roger and I shared a big idea which he executed in a way no one else could have. In addition, Roger was a great patriot who never ceased fighting for his beliefs.’’

Others laid the nation’s political dysfunction and inability to find common ground at his feet, creating the atmosphere for Trump to succeed.

‘‘It’s a very complicated story,’’ said Gabriel Sherman, author of a biography of Mr. Ailes, ‘‘The Loudest Voice in the Room.’’ “He is in some ways a genius and in some ways tragic. His quest for power consumed him.’’

By mid-2016, Mr. Ailes still ruled supreme as he prepared to celebrate Fox News’ 20th anniversary.

But in little more than two weeks, both his legacy and job unraveled following allegations by a former anchor that he had forced her out of Fox News after she spurned his sexual advances. The lawsuit filed on July 6 by Gretchen Carlson quickly triggered accounts from more than 20 women with similar stories of alleged harassment by Mr. Ailes either against themselves or someone they knew.

Despite Mr. Ailes’s staunch denials, 21st Century Fox corporate head Rupert Murdoch and his sons, James and Lachlan, determined that Mr. Ailes had to go.

The allegations went beyond just Mr. Ailes: In April, reports that the network had settled lawsuits with five women who alleged sexual harassment against network star Bill O’Reilly led to his firing. Three other executives also lost their jobs.

His dismissal was a headspinning downfall and a breathtaking defeat for Mr. Ailes, a man who all his life seemed to be spoiling for a fight and was used to winning them.

Mr. Ailes was a brawler. And even when he was on the winning side of a battle, he positioned himself as the defiant outsider going toe-to-toe with his bullying nemeses. Brash, heavyset, and bombastic, he was renowned for never giving in, for being ever confrontational with a chip on his shoulder and a blistering outburst at the ready.

When he founded Fox News Channel, Mr. Ailes’s stated mission was to correct for the sins of a media universe that was overwhelmingly liberal. Pledging fairness from his employees shortly before the network launched, he was typically tough talking: ‘‘Will they hit it every time? Hell, no. Will they try? Hell, yes. Will we be criticized? Hell, yes. Do I care? Hell, no.’’

This attack-dog style served him well when, at 27, Mr. Ailes wrangled a job with Nixon, then vying for a political comeback in the 1968 presidential race.

‘‘Mr. Nixon, you need a media adviser,’’ Mr. Ailes declared (according to Sherman’s biography).

‘‘What’s a media adviser?’’ Nixon asked.

‘‘I am,’’ replied Mr. Ailes, having fashioned the job on the spot.

The remainder of Mr. Ailes’s career would draw on various blends of showmanship, ruthless politics, and an unmatched skill for recognizing TV’s raw communication power before his opponents did, and harnessing it better.

Born in Warren, Ohio, on May 15, 1940, Roger Eugene Ailes described his working-class upbringing with three words: ‘‘God, country, family.’’

Afflicted with hemophilia, he spent much of his early years housebound in front of, and fascinated with, television, and after graduation from Ohio University he landed an entry-level position at a TV station in Cleveland that had just started a local talk and entertainment program starring a has-been former big-band singer named Mike Douglas.

Mr. Ailes went to work as a production assistant on ‘‘The Mike Douglas Show’’ and rose in its ranks along with its rising fortunes as it went into national syndication and moved to Philadelphia.

It was there in 1967 that he and Nixon crossed paths in a meeting that changed both their lives.

As a sign of his versatility, he also became a theater producer, with a hit off-Broadway musical, ‘‘The Hot L Baltimore,’’ in the early 1970s, and a network boss, helping start Television News Incorporated, a short-lived right-wing TV service funded by conservative brewing magnate Joseph ­Coors, that seemed to presage Fox News by a quarter-century.

Mr. Ailes returned to presidential politics in 1984 by helping President Reagan recover from his disastrous opening debate with Democratic opponent Walter Mondale.

And in 1988, he orchestrated the media campaign for Vice President George H.W. Bush’s presidential bid. It was a campaign widely seen as being no less nasty than it was successful.

Within a few more years, he claimed he had sworn off politics.

In 1993, he joined NBC to run its cable business network, CNBC. Meanwhile, he created another network, the talk-and-advice-oriented America’s Talking.

‘‘I’ve gotten over all the cynicism of politics,’’ Mr. Ailes told the Associated Press in 1995, although, during that same period, Mr. Ailes moonlighted as executive producer of the syndicated TV show that starred right-wing radio sensation Rush Limbaugh.

Then, in January 1996, Mr. Ailes resigned from NBC after America’s Talking was sacrificed to free up channel capacity for the company’s cable-news venture, MSNBC.

Within weeks, Mr. Ailes had jumped to what was then known as News Corp., and by fall he launched Fox News Channel.

By 2002, Fox News had sealed the deal as ratings leader, dominating cable-news competition and tying his rivals in knots in both daytime as well as prime time.

From the start, Mr. Ailes steadfastly denied any political bias or agenda on the part of his network, whether in its message or its personnel.

Propelled by Mr. Ailes’s ‘‘fair and balanced’’ branding, Fox News successfully targeted viewers who believed the other cable-news networks, and maybe the media overall, displayed a liberal tilt from which Fox News and Fox Business Channel (which he launched in 2006 against his former business network, CNBC) delivered its audience with unvarnished truth.

Mr. Ailes leaves his third wife, Elizabeth, who had worked for him at CNBC as vice president of programming, and their son, Zachary.