Thirteen campaign workers for Barack Obama yesterday yanked their voter registrations and ballots in Ohio after being warned by a prosecutor that temporary residents can’t vote in the battleground state.

A dozen staffers – including Obama Ohio spokeswoman Olivia Alair and James Cadogan, who recently joined Team Obama – signed a form letter asking the Franklin County elections board to pull their names from the rolls.

The letter – a copy of which was obtained by palestra.net, a Fox News affiliate – came a day after prosecutor Ron O’Brien publicly urged out-of-state campaign workers for both Obama and John McCain to “examine your conscience” before the elections board beings begins opening absentee ballots today.

Earlier in the week, O’Brien spoke with lawyers for both camps and urged them to make sure their staffs met permanent-residency rules, or face possible felony charges.

Also pulling his ballot yesterday was Hofstra University grad Jake Smith, an Obama volunteer who had voted in Knox County, Ohio.

On Thursday, O’Brien cut a deal with 13 out-of-staters, including four from New York, who tossed out their already-cast ballots and admitted they didn’t meet residency requirements.