Utah's "favorite son" presidential candidate Mitt Romney was back on the campaign trail in Salt Lake City Thursday, this time raising money for his former rival, John McCain.

McCain, the presumptive GOP nominee for president, collected some $400,000 at a private fundraiser held at the Grand America Hotel downtown where Romney urged Utahns to support the Arizona senator.

The luncheon event, which cost a minimum of $1,000 to attend and attracted several hundred prominent Utahns, was the first time McCain and Romney have appeared together since Romney endorsed his one-time opponent last month.

While Romney was still in the race, the pair had little good to say about each other. That wasn't the case Thursday now that McCain is counting on Romney to help boost his campaign coffers — and considering Romney as a possible running mate.

"We are united as a party," McCain told reporters at an airport press conference before he and Romney headed off together to another fundraiser, this time in Denver. "What Gov. Romney can play such a huge role in, is that we have to really energize the party."

McCain acknowledged the many people "who committed a great deal" to Romney's now-defunct campaign. In Utah, Romney raised an unheard-of $6 million and won 90 percent of the vote in the state's GOP presidential primary on Feb. 5.

"Having him on board," McCain said of Romney, "is saying to those supporters, 'Look, we as Republicans have to really be energized if we're going to win this election.' That's our challenge now."

Romney, who has spent time at his vacation home in Deer Valley since dropping out of the spotlight, said McCain has been "proven and tested and is an individual who is without question the right person to be the next president of the United States."

He said the support he has received from Utahns, both as a presidential candidate and as head of the 2002 Winter Olympics in Salt Lake City, "is something which is very heartening." Romney returned to Massachusetts after the Olympics, where he served a term as governor.

The pair even joked about Romney's landslide victory in Utah. "That wasn't the only state I lost to Gov. Romney; it was just the largest loss," McCain said of his 5 percent total in Utah. "I was at least hoping to break into the double digits, though."

McCain joked that "after getting over the abject humiliation" of the size of his loss in Utah he understood Romney's appeal in the state because of his role in turning around the scandal-scarred 2002 Olympics.