Sioux City, Iowa (CNN) - South Carolina Gov. Nikki Haley said her decision to endorse Mitt Romney in the Republican presidential race became clear two weeks ago.
At the end of November, Haley ducked out of a Republican Governors Association meeting in Orlando and drove down to Tampa to meet privately with Romney.
There, Haley said she had to ask Romney "some tough questions" about a variety of topics – including the controversial health insurance mandate he implemented in Massachusetts.
"I have talked to him about the health care situation," she told CNN in a phone interview Friday. "He is very aware that that is not something I want in South Carolina."
Haley said Romney assured her that he will grant a waiver to South Carolina to opt out of President Barack Obama's health care law, and said he will push to repeal the law if elected.
She came away from the meeting convinced.
Romney won her over by sounding more like "a leader" than a candidate, explained Haley, who supported the former Massachusetts governor when she was a little-known state legislator in 2008.
"It was at that point, I can honestly tell you, that I knew this was not the same person that I knew in 2008," she told CNN. "You can just sense there is a different feel from him. In 2008, he was a candidate, and the focus was on winning. Now when you talk to him, it's about what he will do, how he can fix this. He has thought a lot about public policy."
"I am strong on standing next to Mitt Romney," Haley added.
Though Haley backed Romney in the last race, since becoming governor in 2010, she has been courted by nearly every GOP candidate and even welcomed several of them to stay overnight at the South Carolina governor's mansion.
Haley said she can sleep at night backing Romney because he is best equipped to fix the three main issues that consume her as governor – "spending, jobs and the economy."
She said Romney would be a better president than the GOP frontrunner, former House Speaker Newt Gingrich, because he has been a governor rather than a member of Congress.
"I didn't want anybody who was involved in anything to do with the chaos that was in Washington," Haley said.
"The biggest contrast is, I want someone who knows how to lead, who has made tough decisions, not just made a vote," she said when asked about Gingrich. "That was really a defining factor. I didn't want anybody that involved in Washington."
Haley harshly condemned Gingrich earlier this year when he questioned Paul Ryan's Medicare reform proposals, and said those comments were a factor in her decision not to endorse him.
She said, though, that she plans to avoid attacking Gingrich or any other Republican candidate as the campaign heats up.
"I don't feel like I have to push down any other candidate to make Mitt look better," she said.
Haley has burnished her national reputation since taking office in January, but her standing among the Republicans who will vote in South Carolina's presidential primary has lately slipped.
A recent Winthrop University poll put her approval rating among Republicans in the state at slightly over 50 percent.
Even so, Haley vowed to campaign at Romney's side when he visits the Palmetto State ahead of the January 21 primary.
She will be with him on Friday at an event in Greenville, and again over the weekend at campaign stops in Charleston and Myrtle Beach.
Despite endorsing him, Haley would not guarantee a Romney victory in South Carolina, where Romney's northern pedigree and evolving positions on core conservative issues have long been viewed with skepticism by many Republicans.
"That's up to the people of South Carolina to decide," she told CNN when asked if Romney will win the state's primary. "He is going to have to continue to work very had to win their support. I am not in the prediction business."