RENO, Nev. – Their goodwill moment gone, President Barack Obama and challenger Mitt Romney plunged back into their acrimonious political campaign on Monday, Obama doubting Romney's readiness to be commander in chief, Romney accusing the president's team of offering "almost all attack ads."

Days after the Colorado movie massacre brought reflection and talk of national unity from both camps, the fight was on again.

Foreign affairs made a rare move to the fore of the campaign as Republican Romney, the former Massachusetts governor, readied for a closely watched trip overseas. Obama, meanwhile, told a military audience that he was the only one in the race with a record, not just words, on international matters as he sought to undercut Romney's travels before they began.