Tens of thousands of poll monitors, challengers, lawyers and other observers are expected to clog voting precincts in battleground states Tuesday in what will probably be the most scrutinized U.S. election in at least 40 years.

Few federal laws govern these largely self-appointed guardians of the voting process, many of whom are brazenly partisan and who range from civil rights advocates to amateur videographers. Many are first-time volunteers, hastily trained by new advocacy coalitions. Others have had no training whatsoever.

Several election directors — including those in swing states — still are drafting ground rules on where monitors can stand, to whom they can talk and how they should report problems. Some guidelines already have been challenged in court.

The confusing rules and lack of federal oversight alarm officials, especially given the intensity of this presidential contest. Particularly in jurisdictions where partisan politics and race have already cleaved deep social divisions, they fear a worst-case scenario where boorish or clueless observers spark a riot.

“People who are doing this care about the election — they’re passionate, and I’d hate to see passion rise to the level of confusion or confrontation,” said DeForest Soaries Jr., chairman of the U.S. Election Assistance Commission, the newly created federal agency in charge of election reform. “They have to remember that one flare-up anywhere in the country could trigger an intense response in multiple places.”

The mobilization may be the single largest election drive since 1964’s “Freedom Summer,” when thousands of college students traveled to the South to help black voters protect their civil rights.

The Election Protection Coalition has registered nearly 15,000 watchers. They’ll focus on 3,500 predominantly African-American and Latino precincts in 17 states.

More than 1,300 computer scientists and other technology professionals have signed up to monitor hardware and software on touch-screen voting terminals through VerifiedVoting.org, a group started by a Stanford University e-voting critic.

The Justice Department is mobilizing, too. It’s dispatching more than 1,000 observers — nearly twice the 516 who monitored the 2000 election. They’ll help secure ballot boxes, set up emergency communications systems and locate backup polling places in case of a terrorist attack or other catastrophe.