Rep. Joe Sestak (D-Pa.) officially launched his long-awaited Senate bid Tuesday, telling the packed crowd at a local Veterans of Foreign Wars hall that his campaign against Sen. Arlen Specter (D-Pa.) will be about putting “principles over politics.—Sestak is expected to make the race a referendum on who the real Democrat is, and in his announcement, the two-term Congressman clearly sought to claim the mantle of change. “In this next election, we Pennsylvanians will vote for a change in accountability to continue that new direction,— Sestak, 57, told the crowd gathered in Folsom, Pa.Sestak has embraced his role as the underdog in an an uphill race that pits him against the White House, Senate leaders and most of the national Democratic establishment, all of whom are supporting the 79-year-old Specter. “While the Pennsylvania Democratic Party welcomes Congressman Sestak to the race, he has an uphill climb against Senator Specter, the incumbent Democrat,— state Democratic Party Chairman T.J. Rooney said in a statement released by the Specter campaign. “Sen. Specter is the front runner and enjoys the full support and financial commitment from President [Barack] Obama, Vice President [Joseph] Biden, Sen. [Bob] Casey and Gov. [Ed] Rendell and thousands of rank and file Democrats.—Specter’s party switch earlier this year provoked Sestak to enter the primary, which is expected to be a nasty and expensive fight.Specter’s campaign reinforced that expectation in their statement responding to Sestak’s entrance into the race.“His months of indecisiveness on his candidacy raises a real question as to his competency to handle the tough rapid-fire decisions required of a senator,— Specter’s campaign manager, Christopher Nicholas, said in a statement. “He hardly deserves a promotion since he has missed 105 House votes this year, which is the worst attendance record of any Pennsylvania Congressman.—Sestak’s Tuesday morning’s kickoff will be followed by two days of stops around the state. He will hold press conferences in Pittsburgh and Johnstown later Tuesday. On Wednesday, Sestak has events scheduled in Harrisburg and Scranton, and then he will end his announcement tour with a studio appearance on “The Colbert Report— that night.The winner of the Democratic race is all but certain to face former Rep. Pat Toomey (R) in the general election. “Pennsylvania Democrats will make an important choice between Joe Sestak, a consistent liberal who really believes in his values, and Arlen Specter, a career political opportunist who believes in nothing but his own re-election,— Toomey’s campaign said in a statement.