The man who tried to lead Republicans toward the White House four years ago flew into South Carolina's crucial battleground and asked voters to give Mitt Romney the next shot.

On a stage set up outdoors at Charles Towne Landing, Arizona Sen. John McCain gave the former Massachusetts governor a hug and an endorsement, saying Romney has the agenda, ideals and public- and private- sector background that "is so badly needed now."

"This man has the experience, talent and the vision to bring America back," McCain told more than 400 who had gathered in the late afternoon.

McCain, who won South Carolina in 2008 en route to winning the GOP nomination, insisted the hard feelings from that campaign -- when Romney was a challenger -- are long dead and buried, and that Romney is the best-positioned Republican to take on Barack Obama in the fall.

"I want to tell you that afterwards, there was no person that worked harder and did more to help me in my quest for the presidency of the United States than Mitt Romney," McCain said of the nominating process last time. "And I will always be grateful for that."

Romney made no mention of his Jan. 21 GOP primary opponents and instead concentrated most of his remarks on Obama, pointing to what he called a mismanagement of the economy, foreign affairs and the administration's efforts to rein in the deficit.

"There's a big gap between what he promised and what he delivered," Romney told the crowd. "What we've seen over the last three years is a failed presidency. I don't think he's a bad guy, I just think he's in way over his head."

It was the pair's first event in the state, and they plan to hold a similar gathering this morning in Conway, near Myrtle Beach. Gov. Nikki Haley, who endorsed Romney last month, was with them.

The only Romney primary foe mentioned during Thursday's appearance was former Pennsylvania Sen. Rick Santorum, who came in a close second in this week's Iowa caucuses. McCain chided Santorum for not getting behind the effort to ban earmarks when he served in Washington.

"Earmark spending is the gateway to corruption," McCain said.

While Santorum was campaigning in New Hampshire on Thursday, he'll make his presence known in South Carolina today by purchasing what was termed a major amount of TV time. The ads will begin airing statewide Tuesday on a frequency that means in-state viewers will see Santorum's message at least 10 times a week.

Romney's appearance came as he began airing an ad in South Carolina that capitalizes on the recent furor over the Obama administration's taking sides in the legal squabble over Boeing's decision to build a new construction facility in North Charleston.

In the ad, Romney takes shots at the National Labor Relations Board and accused Obama of charting a course of labor politics that "affect our economy based not upon what's right for the American worker but, instead, what's right for their politics."

PolitiFact, a voter's guide done by the Tampa Bay Times, said the ad's premise -- that the NLRB tried to prevent Boeing from building its plant in a right-to-work state -- is false. The legal basis for the board's action centered on whether Boeing was punishing a union for staging strikes, not that Boeing opened a factory in a right-to-work state, it said.

The ad comes a day after the administration used the congressional recess to put three new appointments on the labor board. Outside shots of a Boeing plant are seen in the 30-second spot. The NLRB and Boeing resolved the dispute last month.

Haley said Romney has to work to win South Carolina and should emphasize his support for the line-item veto and his opposition to Obama's health care reform. "The only thing he's got to do is get his message out," she said. "The only thing he's got to do is make sure boots are on the ground."

Romney's appearance drew Republican voters from far and wide, including Tom Grewenig of Beaufort, who said he is warming to Romney. "I think we're moving more toward Romney because of what's happening, that Newt (Gingrich) is exploding," he said.

But not everyone present was committed to Romney.

K.C. Lombard, a board member of the Charleston Tea Party, said he was just there to see Romney up close. "My preference is anybody but Romney, but if he's elected (the GOP nominee), I'll be involved," he said. "He's better than what we've got."

One protester shouted at Romney, "What happened to American Pad and Paper Co.?" The Indiana company was bought by Romney's company, Bain Capital in 1994, and dozens of its workers were laid off.

Former U.S. Rep. Henry Brown also was at the gathering and said he is 90 percent committed to Romney, and hinted he expected the race to get more heated, specifically pointing at the outspoken Gingrich.

"Newt has already decided to show the other side of Newt," he said. "So we'll see how far that goes and how it resounds in South Carolina."