GREENVILLE, S.C. - In a standing-room only fire station in South Carolina this afternoon, Gov. Nikki Haley made her endorsement of Gov. Mitt Romney official, declaring that he is "already a leader" who is ready to take over the White House.

"I am very impatient by nature. And it is not what you say, it's what you do. I wanted someone who had proven results," said Haley, who appeared with husband Michael and Ann and Mitt Romney. "[Romney] is no longer a candidate trying to win. He's a leader who knows what he wants to do his first day in office and is ready to do it."

The Haleys and the Romneys took the stage to a rock star-like reception, the crowd cheering as Haley asked supporters to deliver a "South Carolina welcome."

"It is with great pride, great respect, great support, that Michael and I are very proud to say that we are endorsing Gov. Mitt Romney for President of the United States," Haley said.

"What I've missed is having a partner in Washington and having a partner in the White House and what I'm looking for is a partner I can have now.

"When we did the process of elimination, one thing I knew we couldn't have is anyone associated to the chaos, which is Washington D.C.," she said. "So we started eliminating from there and when I was looking at Gov. Romney, it's not about what he's said, it's what he's done."

Haley described a meeting with Romney, during which she told him she had some "tough questions" to ask him. She said she wanted to be assured that he wouldn't let an individual health care mandate come to South Carolina, and he did.

"The icing of the cake was the one candidate President Obama continues to go after is Gov. Romney, and that says something," Haley said of making her decision to back Romney. "That says that's who he considers to be a real threat."

Romney was gleeful during Haley's endorsement, explaining how he woke up this morning in Iowa with a "huge smile on his face" that grew even larger when he saw Haley on Fox News during his morning workout talking about endorsing him.

"A lot of us stood at her door," Romney said of Haley, "hoping to win her endorsement."

Haley's own poll numbers in the state call don't show overwhelming popularity, though. The latest numbers from Winthrop University show that her approval rating among registered voters is at 35 percent, which is lower than President Obama's 45 percent approval rating. Among Republicans, Haley's approval rate is just over 50 percent.

Even so, Romney was downright giddy about the endorsement.

"We've been hoping for this for a long, long time," he said.

Haley, asked later by the press whether she believes Romney's Mormon faith will be a factor among the evangelical voters in the Palmetto State, she said that it was "not going to be an issue."

"The reason I know why [it won't be an issue] is because South Carolina just elected a 38-year-old Indian female for governor of South Carolina," Haley said. "What the people of South Carolina care about are values, and family and faith and what you do and results and I think you can look at the Romney's and you can see this is a family of faith, this is a family of values, and a source of pride for anything they've ever done. I have faith in the people of South Carolina, that's not going to be an issue."

Haley explained Speaker Newt Gingrich's sudden rise in the polls in South Carolina as a result of his campaigning in the state and added that she and Romney have discussed their own campaign strategy in the state.

"Once his message gets out there, I know the people of South Carolina [will be] excited about it," Haley said.

And Romney's message started airing on television today, as the campaign launched its first television ad in the Palmetto State. The ad, "Leader," is the same ad that has been running in Iowa and New Hampshire, and highlights Romney's family life.

Haley will join Romney Saturday at two town halls, in Charleston and Myrtle Beach.