Michele Bachmann already sent her bus driver home for Christmas. So with the coach parked in a Des Moines lot, she rolled across rural southern Iowa today in an SUV, the only Republican presidential candidate still campaigning in the state.

She greeted voters in coffee shops, taped short videos, and fielded questions from a small handful of journalists who followed her under clear skies, on mostly empty roads. Speaking to reporters in Chariton, the Minnesota congresswoman called the House deal to extend the payroll tax break a “mistake,’’ because it will reduce the flow of money into the Social Security trust fund.