(Patrick Collard ~ Associated Press)
"Today, I have withdrawn my candidacy for president of the United States.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 have won in the six states that have voted.
In Florida, McCain, former Massachusetts governor Mitt Romney and former New York mayor Rudy Giuliani are battling for the lead ahead of its Jan. 29 primary, while former Arkansas governor 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.