"It's purely social," said Mark Salter, a senior adviser to McCain.
Florida Gov. Charlie Crist, Louisiana Gov. Bobby Jindal and former Massachusetts Gov. Mitt Romney were all invited to a Memorial Day gathering at the senator's home in Sedona, Ariz. Romney ran for the Republican presidential nomination in last winter's primaries, but dropped out months ago and has endorsed McCain.
They were among the estimated two dozen people - including some 10 couples - invited. McCain often hosts friends and political acquaintances at his compound.
McCain said more than a month ago that he was in the "embryonic stages" of selecting a running mate for the fall campaign, but neither he nor aides have disclosed additional information in the weeks since.
It will be the first visit to Sedona, Ariz., for all three.
The New York Times reports that Gov. Tim Pawlenty, R-Minn., who has also been mentioned as a contender to run with McCain, is not going to Arizona and that his associates said he had a wedding on Saturday.
Romney dropped out of the race in February after it became apparent it would be near impossible to topple McCain in the convention delegate race. He endorsed the Arizona senator a week later and pledged to help him win the nomination.
Since then, McCain has praised Romney repeatedly as someone who is certain to continue playing a large role in the GOP. Romney, for his part, has suggested that he'd accept a vice presidential slot, though some Republicans privately speculate that he's looking ahead to a possible repeat run in 2012.
Neither man appeared especially fond of the other during the campaign. Romney cast McCain as outside of the GOP's conservative mainstream and a Washington insider who contributed to the problems there. McCain, in turn, argued that Romney's equivocations and reversals on issues indicated a willingness to change his positions to fit his political goals.
Crist, 51, provided a major boost to McCain prior to Florida's Jan. 29 primary with a well-timed endorsement.
Elected governor in 2006, Crist has been seen as a moderate Republican. He has championed efforts to curb climate change, and was praised by former President Clinton for his efforts to restore voting rights of felons who have completed their sentences.
He also pushed for a law that requires a paper trail in state elections, a measure that bans the electronic voting machines his predecessor, Gov. Jeb Bush, sought after the 2000 presidential election. That election ended in a hotly contested recount, which President Bush won by 537 votes.
Jindal, 36, son of Indian immigrants, was elected governor of Louisiana in October 2007, three years after being elected to the House, where he was credited with playing an important role as his state recovered from Hurricanes Katrina and Rita. Previously, he was secretary of Louisiana's health department, and an assistant secretary in the U.S. Department of Health and Human Services.
Jindal's spokeswoman, Melissa Sellers, downplayed the visit and did not mention the vice presidential search. She said the governor and his wife were going to Arizona to "spend time" with McCain and his wife, Cindy, and noted that that two lawmakers have met several times before.
Among other guests expected were Sens. Joe Lieberman, I-Conn., and Lindsey Graham, R-S.C., close confidantes of McCain.