DAYTON, OHIO - Mitt Romney ambled through the exhibits at the InfoTech 2010 conference here the other day, shaking hands, posing for photos, sneaking an occasional chocolate turtle and, ever the salesman, promoting the candidacy of yet another Republican candidate. On this trip, he was stumping for Rob Portman, the Republican Senate candidate who is heavily favored to win his race Tuesday. Romney was self-effacing as he moved along the rows of exhibits. "This is Rob Portman, he's running for Senate," he said as he introduced the former congressman to a group at one exhibit. "I'd love for you to...