S.C. Gov. Nikki Haley endorsed Mitt Romney this morning for president, calling him a candidate of courage who cut taxes and balanced budgets while leading Democrat-controlled Massachusetts as governor.

Romney is "someone who knows what it's like to lead and make a decision, not just to take a vote," she said during a 7:15 a.m. appearance on Fox and Friends.

The backing gives Romney an important boost ahead of South Carolina's Jan. 21 primary. The state has correctly picked every GOP nominee since 1980.

Romney is heading to South Carolina this weekend, where he's likely to be joined by Haley at town hall meetings on the coast, including in Charleston. As a state representative, Haley backed Romney in 2008.

Haley said every candidate in the field sought her endorsement, except Ron Paul, whom she said never attempted to reach her.

She also noted the field is not ideal for everyone in the party, but is working toward a November showdown against Barack Obama.

"You put all those candidates together and you have a perfect candidate," she said.

Romney is the candidate most cited as a threat to the president's re-election, Haley said. "That lets me know he's scared of him," she said.

The endorsement comes as a recent poll shows Haley's popularity is falling in the state, even among her own party, according to Winthrop University.

Only 34.6 percent of those surveyed — 1,073 registered S.C. Democrats, Republicans and independents — said they approved of Haley's job performance, according to the results released this month.

Haley's approval rating is lower than that of President Barack Obama, a Democrat, the survey found. Obama has a 44.8 percent approval rating in strongly Republican South Carolina, according to Winthrop.

Romney and Haley will make a joint appearance at 4:30 p.m. today at Boiling Springs Fire Station, 208 Blacks Drive in Greenville.

The two will visit the Lowcountry Saturday with a 9:15 a.m. town hall in Memminger Auditorium, 56 Beaufain Street in Charleston and a 2:20 p.m. town hall at Horry-Georgetown Technical College, Grand Strand Campus Conference Center, 743 Hemlock Avenue in Myrtle Beach.

UPDATE:

CNN has reported that Haley recorded a robo call for Romney that has gone out to voters today.

During the call, Haley says, according to CNN, "Hi, this is Governor Nikki Haley, and this morning I announced my endorsement of Mitt Romney for President of the United States."

She continues, "Mitt Romney knows what it means to make decisions, real decisions, not simply cast a vote. He is not a creature of Washington. He knows how the private economy works, how to fix it, and most importantly how to solve problems. And he has proven it."

Listen to an audio clip of the call, from CNN.com