For the first time since the 2006 election cycle, Sen. John McCain's (R-Ariz.) name won't appear on a ballot this fall.

This time, his role is as a surrogate for Mitt Romney and for GOP congressional candidates hoping that McCain can give them a boost. And there are several reasons to think the Arizona senator can still make a positive difference.

(Johannes Simon/Getty Images)

One is name recognition. Having waged two presidential campaigns, including one as the Republican nominee in 2008, McCain remains one of the best-known Republicans in the country. That makes him a useful ally for congressional candidates looking to build momentum — or draw attention to their campaigns.

One such candidate is Mia Love, a conservative Republican running against Rep. Jim Matheson (D-Utah). If elected, Love would be the first black Republican woman in Congress.

McCain stumped for Love in Utah on Thursday. "People who come to Washington, if they have some gravitas associated with them, like she does — she will be an instant star — and that will give her the ability to work to get things done," he told the Salt Lake Tribune. That quote is a valuable asset for Love, who can use it to show donors that her campaign has attracted the attention of a veteran legislator.

On Friday, McCain is fundraising in Montana for Rep. Denny Rehberg, the Republican trying to dislodge Democratic Sen. Jon Tester from office. McCain raised money for Sen. Scott Brown (R-Mass.) this summer.

And, earlier this week, he was part endorser and part political referee when he waded into a race in his home state.

McCain officially picked sides in the contest pitting freshman Republican Reps. Ben Quayle and David Schweikert. Decrying a Schwiekert mailer that says Quayle "goes both ways" (a phrase Quayle's campaign says has sexual connotations, but Schweikert's argues is simply a flip-flop charge), McCain endorsed Quayle. "This crosses the boundary of decent political dialogue and discourse. This is not something that is acceptable at all," McCain said of the mailer.

McCain will speak at the Republican National Convention later this month, where his military and foreign policy experience could appease undecided voters who are leaning toward Romney on economic issues, but are concerned about the former Massachusetts governor's lack of military experience and thin foreign policy résumé. McCain is the ranking Republican on the Senate Armed Services Committee and a former prisoner of war.

"I think you can expect [the convention speech] in part to focus on national security," said a McCain aide.

McCain's status as a senior member of the GOP is a testament to his political survival, which is due in part to changing views that have transformed him from a "maverick" independent to a conservative, and now, back in the other direction.

In 2010, McCain faced a primary challenge from former congressman J.D. Hayworth, whose candidacy came to symbolize a fight against everything Arizona conservatives disliked about McCain's record. Faced with the threat, McCain took a sharp right turn, summed up neatly by his rating as the most conservative member of the Senate in 2010, according to National Journal's vote ratings. Earlier in the decade, McCain ranked much closer the the middle. In 2011, the year after his reelection, he was the 16th most conservative member of the upper chamber.

The shine on McCain's maverick image may have worn off some, but he remains a major figure within the GOP, one who can draw positive press coverage and help, in some cases, serve as a verifier of a candidate's bona fides on issues. As long as those things are still true, McCain will have his niche in the party.