NAPLES, Fla. (AP) – Republican Fred Thompson, the actor-politician who attracted more attention as a potential presidential candidate than as a real one, quit the race for the White House on Tuesday after a string of poor finishes in early primary and caucus states.

“Today, I have withdrawn my candidacy for president of the United States. I hope that my country and my party have benefited from our having made this effort,” the former Tennessee senator said in a brief statement.

Thompson’s fate was sealed last Saturday in the South Carolina primary, when he finished third in a state he had said he needed to do well in, if not win.

In the statement, Thompson did not say whether he would endorse any of his former rivals. He was one of a handful of members of Congress who supported Arizona Sen. John McCain in 2000 in his unsuccessful race against George W. Bush for the party nomination.

Thompson, best known as the gruff district attorney on NBC’s “Law & Order,” placed third in Iowa and South Carolina, two states seemingly in line with his right-leaning pitch and laid-back style, and fared even worse in the four other states that have held contests thus far. Money already tight, he ran out of it altogether as the losses piled up.

Thompson, 65, exits the most wide open Republican race in half a century; three candidates each having won in the six states that have voted.

In Florida, McCain, former Massachusetts Gov. Mitt Romney and former New York Mayor Rudy Giuliani are battling for the lead ahead of its Jan. 29 primary, while former Arkansas Gov. Mike Huckabee evaluates his next steps amid money troubles.

In an interview Tuesday, Huckabee suggested he would have beaten McCain in South Carolina if Thompson had dropped out earlier.

“The votes that he took essentially were votes that I would have most likely had, according to the exit polls and every other analysis,” Huckabee said on MSNBC.

Despite initial impressions that Thompson could garner strong conservative support, it never materialized. He never won backing from more than one in five conservatives in any of the earliest primaries and caucuses, including the 19 percent who exit polls for The Associated Press and television networks showed supported him in South Carolina. His showings were similarly weak with white born-again and evangelical Christians.

In New York, McCain told The Associated Press: “Fred Thompson ran an honorable campaign. He and I will remain close friends, and I wish him and his family the best.” He later told reporters he didn’t think Thompson would endorse anyone.

Romney commended Thompson’s candidacy.

“Throughout this campaign, Fred Thompson brought a laudable focus to the challenges confronting our country and the solutions necessary to meet them,” Romney said in a statement. “He stood for strong conservative ideas and believed strongly in the need to keep our conservative coalition together.”

Thompson’s withdrawal capped a turbulent 10 months that saw him go from hot to not in short order.

He began toying with a presidential run last March, emboldened by a fluid Republican nomination fight and a restive conservative GOP base. He also was charmed by resounding calls for him to get into the race — and his meteoric springtime rise to the top of national and state polls.

Fans trying to draft him as a candidate launched an online effort, seizing on his conservative Senate voting record as well as his lumbering 6-foot-5 frame and deep baritone as they argued he was right out of central casting. They painted him as the second coming of Ronald Reagan and the would-be savior of a Republican Party demoralized after electoral losses in 2006 at all levels of government.

Expectations rose higher — and his standing in polls started to fall as he failed to meet them.

Thompson played coy about his intentions all the while taking steps to prepare for a formal entrance into the race with a flourish. He cut ties with NBC, visited early voting states and delivered high-profile speeches. And, he started raising money and set up a preliminary campaign organization.

He delayed his expected summertime entrance in the race until fall, perhaps missing an opening created by McCain’s near campaign implosion.

As he prepared to officially join the race, Thompson was plagued by lackluster fundraising; high-profile staff departures, including some prompted by his wife Jeri’s involvement in the campaign, and less-than-stellar performances on the stump. Thompson also endured repeated questions about his career as a lobbyist and his thin Senate record.

Thompson formally announced his bid in early September, but hit a rocky patch from the get-go. He skipped a Republican debate in New Hampshire, annoying some in the state, to announce his candidacy on NBC’s “Tonight Show” with Jay Leno.

His easygoing style and reputation for laziness translated into a light campaign schedule that raised questions about his desire to be president. A spate of inartful answers to campaign-trail questions — on everything from the Terri Schiavo case to Osama bin Laden — didn’t help matters.

Though his star had faded, Thompson earned positive reviews for a series of debate performances last fall and earned an endorsement from the National Right to Life Committee.

Thompson first made a name in Washington politics three decades ago when he served as minority counsel to the Senate Watergate Committee. Thompson, who was 30 at the time, was appointed to the high-profile job by his political mentor, then-Sen. Howard Baker of Tennessee, who was the top Republican on the committee. Thompson had managed Baker’s re-election campaign and had been an assistant U.S. attorney in Nashville.

Thompson asked one of the key questions of the Watergate hearings: “Mr. Butterfield, are you aware of the installation of any listening devices in the Oval Office of the president?”

Butterfield’s reply was the first time the public learned that President Nixon had been secretly taping his conversations. But Thompson, who knew the answer before he asked his famous question, had tipped off the White House before the hearing that the committee had discovered the existence of the tapes.

Several years later while practicing law in Tennessee, Thompson represented Marie Ragghianti, the head of the Tennessee Parole Board who was fired after exposing a pardon-selling scheme involving aides for then-Gov. Ray Blanton. Thompson played himself in the 1985 movie “Marie” based on the episode and got generally positive reviews.

The film launched Thompson’s acting career. Among his many characters, he played President Ulysses S. Grant in last year’s made-for-TV HBO movie “Bury My Heart at Wounded Knee,” and the fictional President Charles Ross in the 2005 film “Last Best Chance.”

Thompson was elected in 1994 to the Senate to fill the unexpired term of Al Gore, who had been elected vice president. He easily won re-election in 1996.

During his eight years in the Senate, Thompson was considered a reliably conservative vote.

A couple of months after his 38-year-old daughter died of a heart attack, Thompson announced he would not run for re-election in 2002.

In April of last year, Thompson disclosed he had been diagnosed in 2004 with non-Hodgkin’s lymphoma, a highly treatable form of cancer.

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Associated Press Writer Joan Lowy in Washington contributed to this report.