New Mexico Gov. Bill Richardson dropped his bid for president Thursday in Santa Fe without offering his endorsement to any of the remaining Democratic candidates.

Richardson ended his campaign following back-to-back fourth-place finishes in the Iowa caucuses and New Hampshire primary. He had been unable to break through the pack of his better-known, better-funded Democratic competitors.

But despite having worked in Bill Clinton's cabinet, he did not throw his support behind Hillary Clinton, or any other candidate.

"I would urge those who supported my candidacy to take a long and thoughtful look at the remaining Democrats," he said. "They're all strong contenders who each in their own way would bring desperately needed change to our country."

Richardson said that although his support at the polls lagged the front-runners, many of his leading rivals moved closer to his positions on such issues as the war in Iraq, energy and education.

"I'm just happy I altered the shape of the debate," Richardson told FOX News afterward. "I'm not retreating to obscurity."

Asked on FOX News whether he'd be interested in jumping on as a running mate during the general election, Richardson repeated: "I'm happy where I am."

Click here to see Richardson's interview on FOX News.

Clinton's campaign announced shortly after Richardson formally dropped out that two of his supporters, former Ambassador Edward Romero and former U.S. Housing Secretary Henry Cisneros, were backing her candidacy.

Clinton also offered a statement on the governor's departure from the race.

"Governor Richardson is a great public servant and a friend. He waged a hard-fought and substantive campaign, and helped drive the conversation on the great issues facing our nation. I wish him the best of luck as he continues his outstanding work in New Mexico," she said.

In Santa Fe, Richardson urged the Democratic candidates not to resort to "personal attacks" on the trail, and said he is now "returning to a job that I love."

He said as governor he would continue to push for universal health care coverage in New Mexico. The state's legislature convenes for its one-month session Tuesday.

"It is with great pride, understanding and acceptance that I am ending my campaign for president of the United States," he said. "It's been an exhilarating and humbling year, an experience that I will treasure and never forget."

Richardson came to the race with one of the most wide-ranging resumes of any candidate to run for the presidency, bringing experience from his time in Congress, President Clinton's cabinet and the New Mexico statehouse as well as his unique role as a freelance diplomat. As a Hispanic, he added to the unprecedented diversity in the Democratic field that also included a black and a woman.

But Clinton and Barack Obama dominated the spotlight in the campaign, and Richardson was never able to become a top-tier contender. He accused his rivals of failing to commit to bring troops home from Iraq soon enough.

Democratic candidate John Edwards, who pledged to soldier on after a third-place finish in New Hampshire, praised Richardson upon learning he would drop out.

"He was a very good candidate, a serious candidate. He ran a good race. I congratulate him. He ought to be proud of what he's done. I think what it means is here in South Carolina, we're going to have three candidates who are running really vigorous campaigns for the voters to choose from," he said. "So there is becoming - what's happened is over time the race is becoming more focused. I think that's good for the democracy. I think this thing's going on for a long time. I assume the other two are. I know I am. I'm in it for the long haul."

Clinton said in a statement that, "Governor Richardson is a great public servant and a friend. He waged a hard-fought and substantive campaign, and helped drive the conversation on the great issues facing our nation. I wish him the best of luck as he continues his outstanding work in New Mexico."

Delaware Sen. Joe Biden and Connecticut Sen. Chris Dodd also dropped out of the race after distant finishes in the Iowa caucuses Jan. 3.

Richardson portrayed his campaign as a job application for president, and ran clever ads that showed a bored interviewer unimpressed with his dazzling resume. The commercials helped fuel his move to double-digit support in some early state polls, and advisers argued he was poised to move past former vice presidential nominee John Edwards for the role of third-place challenger.

But he was not able to build the momentum and came in a distant fourth place in Iowa and New Hampshire. Richardson didn't get quite 5 percent in the New Hampshire primary Tuesday and came in with just 2 percent in the Iowa caucus last week.

FOX News' Cristina Corbin and The Associated Press contributed to this report.