Pat Caddell, the pollster responsible for Jimmy Carter’s win who later backed Donald Trump, died Saturday at the age of 68.

Caddell died in Charleston, South Carolina, from complications stemming from a stroke, the New York Times reported.

He got his start in politics as a 21-year-old Harvard University senior working as a campaign adviser and pollster for left-wing populist Sen. George McGovern’s campaign to secure the 1972 Democratic Party nomination.

McGovern lost in a landslide to Republican President Richard Nixon, but Caddell used his acumen for translating voter data into political strategy for other clients.

The self-taught pollster became one of then-former Gov. Jimmy Carter’s key advisers, eventually ushering him into the White House.

Caddell advised Carter to be broad with his themes and not to “substitute substance for style.”

After Carter’s 1976 win, Caddell became known nationwide as the guy who could take the temperature of the American electorate. He stayed on as an adviser during Carter’s presidency, and remained active in the political scene.

In the 1990s, Caddell turned away from the Democratic Party for its shunning of populism in favor of big business.

He spent the latter part of his career as a Fox News pundit, Breitbart News contributor, an adviser to former White House chief strategist Steve Bannon, and was one of the few pollsters who backed Donald Trump in the 2016 election.

Caddell said at a conference in November 2017 that Trump was successful because he was able to tap into the anti-establishment sentiment building during the 2016 presidential election, adding that Trump’s “Make America Great Again” slogan “was the greatest slogan of my lifetime.”

Caddell is survived by his daughter, Heidi Caddell Eichelberger; his three grandchildren; his brother, Daniel Caddell; and his sister, Patricia Roberts.