ASK GEORGE ALLEN IF HE'S RUNNING for president, and Virginia's junior senator demurs like any politician facing re-election this year. "When we get to the future, I'll determine the future," he told reporters recently. But make no mistake -- George F. Allen is running for president. Or he just happens especially to enjoy primary states. In March and April, he visited Iowa, New Hampshire, Texas, South Carolina, and North Carolina. He's courting bigwigs at state party conventions, and throwing his name in the hat for presidential straw polls. Facing two serious Democratic challengers while his re-election poll numbers hover around...