(CNN) -- Former Arkansas Gov. Mike Huckabee bowed to "the inevitable" and dropped out of the Republican presidential race Tuesday night after an improbable run for a politician little known beyond his home state a year ago.

Huckabee announced he was giving up his bid for the White House after John McCain swept Tuesday's contests in Texas, Ohio, Vermont and Rhode Island, giving the Arizona senator the delegates needed to claim the party's nomination in September.

"It's been a heckuva run," he said.

Huckabee urged his supporters to back McCain in November and said he has no "Plan B" for his political career. Watch Huckabee concede race »

"Clearly, things didn't go our way tonight, and we had hoped they would," he told reporters on his plane back to Little Rock. "But when the inevitable is staring you in the face, you accept it."

When Huckabee announced his candidacy in January 2007, the former Baptist pastor was best known for his dramatic weight loss. The 52-year-old governor dropped more than 100 pounds after being diagnosed with diabetes in 2003, and wrote a 2005 book called "Quit Digging Your Grave with a Knife and Fork."

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