What's the Matter With Obama By Robert D. Novak Monday, April 21, 2008; Page A15 Traveling the country the past few months, I have encountered habitual Republican voters so entranced by Barack Obama's potential to lead the nation that they plan to vote for him in November. Once Hillary Clinton's supporters return to the fold, Obama Republicans could produce a Democratic presidential landslide. But Obama's recent missteps jeopardize their support and imperil his election. These apostate Republicans were never deluded into considering him anything other than a doctrinaire liberal who wants a more intrusive government, with higher taxation and tougher regulation. But they have leaned toward him as an exceptional candidate in the mold of John F. Kennedy and Ronald Reagan, a post-partisan leader and a welcome contrast to George W. Bush's failed presidency. That impression is threatened by Obama's performance the past 10 days, climaxing in Wednesday night's debate