SAN DIEGO (AP) -- A 26-year-old T-shirt designer could turn San Diego's mayoral election on its head.

Eric Bidwell, who's running on a self-described ''revolutionary'' platform, is the dark horse in Tuesday's race against incumbent Jerry Sanders and millionaire businessman Steve Francis. Bidwell may draw enough support to force a runoff between the two Republicans; the top two finishers will have to face off in November if no one wins a majority in the nonpartisan contest.

Without spending a cent, the dreadlocked Bidwell has created some of the campaign's memorable moments. At one of the final debates before election, he told television viewers that Sanders' campaign manager gave him a script of ''gnarly'' talking points to trash Francis. The campaign manager promptly resigned.

The nation's eighth-largest city is no stranger to colorful candidates. Councilwoman Donna Frye, a Surf-shop owner and wife of legendary surfer Skip Frye, almost won on a write-in campaign in 2004, losing only after courts invalidated ballots on which voters wrote her name but failed to darken the adjoining ovals.

Neither Sanders, an affable former police chief, nor Francis, who made his fortune as founder of a hospital staffing company, has generated much excitement.

Sanders provided one of the campaign's more dramatic moments when he cursed at Francis rather than accept his handshake after a debate in April. Sanders later apologized, but criticized Francis for ''tattling'' to reporters.

Sanders, 57, says he deserves a second term to continue the city's financial recovery that he helped lead.

Francis, 53, has embraced a vague ''change'' mantra. He ran on a socially conservative platform in 2005, when he placed third in a special election to replace Mayor Dick Murphy, who resigned suddenly amid federal investigations of whether city officials hid mammoth pension obligations from public view.

''This is not a town that has ever been big on burning down the town hall and storming the Bastille,'' said Carl Luna, a political science professor at San Diego's Mesa College who has moderated several mayoral debates. ''Sanders hasn't been able to find a good narrative about why he should be re-elected, except that things are going pretty well, and Francis is not advancing a vision of why him as opposed to Sanders.''

City services have continued to deteriorate during Sanders' tenure, with potholes going unfilled and water mains regularly breaking. But under his watch, Standard & Poor's recently restored the city's credit rating, ending a virtual freeze on its ability to borrow money.

Francis, who in 2006 liquidated $52.3 million in stock of his company, AMN Healthcare Inc., has enough money to continue his media campaign if Sanders falls short of a majority. Sanders has raised $426,000 this year from hundreds of individual donors.

''Francis' best chance is to keep it alive into the fall,'' said Luna.