WASHINGTON — Patrick Caddell, the pollster who helped propel Jimmy Carter in his longshot bid to win the presidency and later distanced himself from Democrats, has died, a colleague said. He was 68.

Caddell died Saturday in Charleston, South Carolina, after suffering a stroke. That's according to Professor Kendra Stewart of the College of Charleston, who confirmed the death to The Associated Press.

After working with Democrats in the 1970s and 1980s, Caddell eventually drifted away from the Democratic Party and began advising supporters of Republican Donald Trump, including a close relationship with former Trump campaign strategist Steve Bannon, and was a contributor to Fox News for a time.

Caddell worked for 1972 Democratic nominee George McGovern, then joined with Carter in the mid-1970s to develop a campaign strategy to overcome the cynicism spawned by the Vietnam War and Watergate. In an oral history for the University of Virginia's Miller Center, Caddell said Carter's best bet was to present himself as an outsider who could help heal the country.

Carter expressed his gratitude through a spokeswoman.

"Pat Caddell was a brilliant pollster who at a young age provided me with key information and over his career helped to shape the future of professional research," Carter said in a statement. "Rosalynn and I are grateful for his counsel in our campaigns and while we were in the White House. We send our prayers to his family and friends."

As a student at Harvard, Caddell had studied Southern politics and was helpful to Carter and his close advisers as they studied how to maneuver their campaign between the competing forces of the McGovern liberals and supporters of conservative firebrand George Wallace.

Caddell, a native of Rock Hill, South Carolina, and the Georgia governor found they had many ideas in common about how he could win the presidency. As a one-term governor from the South, Carter would have to offer a compelling outsider theme.

"In order to win, he had to articulate a sense of what had happened to the country through Vietnam and Watergate. If you go back and look at those speeches that he gave early in the campaign, he would talk about the damage to the country, its psychology," Caddell said in the oral history. "Essentially, what he was running on in the campaign was that the country had been psychologically devastated by the previous decade of events. He was offering himself as a healer..."

Carter won the presidency, but Caddell, known for a time for his bushy black beard with a gray streak, preferred to advise the president from outside the White House.

Caddell warned Carter of the dangers of getting out of touch with the voters who had embraced him during the campaign. But one bit of Caddell advice seemed to backfire.

Caddell wrote a memo warning of crisis of confidence that Americans were experiencing and urged Carter to address them directly about it. That became known as the "malaise" speech, though Carter never used that word.

He lost re-election a year later, in a bid complicated by economic fears, an intraparty challenge and the Iran hostage situation. The winner, Ronald Reagan, offered an optimistic vision of the country.

Caddell consulted with other Democratic presidential candidates in the 1980s and was a close adviser to Joe Biden during his failed 1988 bid for the presidency.

In explaining his break from Democrats, Caddell said he thought the party was no longer "a party of the people" but had been hijacked by elites, the well-educated, Wall Street and interest groups.

He noted in a 2016 speech to students at Michigan's Hillsdale College that he was offended when the Democrats at their national convention would not allow Pennsylvania Gov. Bob Casey Sr., who was against abortion, to deliver a convention speech. Caddell considered the Democrats to be guilty of "the stifling of dissent."

And he commended Trump for reaching out to people the Democrats were not effective in reaching, and his willingness to take on "the political class."

Stewart said Caddell died early Saturday at the hospital and had not been ill, so it was a surprise to those who knew him.

Among his many projects, he was a guest lecturer at the College of Charleston and the Citadel, she said.

"After escaping Washington, he sought refuge in L.A., where he was a writer and producer on 'West Wing' with Aaron Sorkin and consulted on other films such as 'Outbreak,' 'Air Force One' and 'In the Line of Fire,'" Stewart said.

"These past years he has been consulting, conducting research and writing on the state of voter unrest and dissatisfaction with the political system. I worked with him through his company, Caddell Associates, on many of these projects," Stewart said. "He was a passionate man who wanted nothing more than to leave his grandchildren a better country."