When John McCain arrives this afternoon for a town hall at Nashville's Ryman Auditorium, he'll do the usual: give a little speech, take a few questions, joke that he's "older than dirt" and accuse Barack Obama of wanting to give Iran's Mahmoud Ahmedinejad a back rub. But seeing Nashville is Music City and the Ryman is the original home of the Grand Ole Opry, he'll also have a little surprise up his suit sleeve, according to Politico's Jonathan Martin: a musical performance by John Rich. As in, one half of the country duo Big & Rich--the people responsible for the song "Save a Horse (Ride a Cowboy)."

For most general-election presidential candidates, such a setup wouldn't sound particularly weird. But as far as I can tell, Rich's appearance marks the first time this cycle that a musical act has opened for John McCain on the trail. Where's the love?  Neither Obama nor Hillary Clinton has had any difficulty recruiting rock stars to their cause: so far, Will.i.am, Arcade Fire, the Decemberists, the Grateful Dead, Macy Gray and Wilco have serenaded Obama's fans, and Hillary has Ricky Martin, Janet Jackson, Madonna, Carly Simon, Tony Bennett, Jon Bon Jovi, Melissa Etheridge and Carole King on board. In contrast, McCain claims but a single prominent musical supporter: California pop maestro Burt Bacharach. Unfortunately, a largely Democratic octogenarian composer and one member of an unorthodox country duo do not a showstopping GOP concert lineup make. Even worse: John Mellencamp and ABBA actually blocked McCain from using their songs at campaign stops.

(On the bright side, McCain's daughter Sidney is a longtime music exec who has represented the White Stripes, Grandaddy, Moby, Stereophonics and Spritualized. So if anyone can hook him up, she can, right? Not so fast: even Sid's a Democrat. Figures.)

Now, it's not like celebrity endorsements translate into votes. In fact, the Annenberg Public Policy Center found in March that "the endorsement of presidential primary candidates by notable groups and individuals carries little weight with the public." But famous musicians can help in other ways--namely by raising money. In 2004, Bruce Springsteen, who now supports Obama, raked in more than $10 million for John Kerry with an October swing-state tour, and this April a pro-Clinton Elton John concert vacuumed up $2.5 million in one night. Trailing Obama by $144 million in the money race, McCain could use that kind of assistance. Big & Rich? Not big or rich enough.

The problem? He may not get it anytime soon. In 2000 and 2004, the twangy, evangelical George W. Bush boasted his fair share of backing bands. But nearly all of them were either Christian (Third Day, Michael W. Smith), country (Travis Tritt, Larry Gatlin, Billy Ray Cyrus) or ultra-conservative (Ted "The Motor City Madman" Nugent). A relative moderate, McCain isn't particularly comfortable with any of those constituencies--and more importantly, they're not particularly comfortable with him. What's more, with his musical tastes formed largely in 1950s, McCain's going to have a tough time finding favorite acts that are still lively enough to spice up his rallies--let alone still alive. As the pro-gun Nugent has written, "McCain's advisers had better figure out how to sing to the conservative base real quickly or he does not stand a chance at winning." For now, at least, they'll be the only ones doing any singing.