Bret Schundler by a mile.
Schundler started out his political career as a left-wing Democrat. He worked in the 1984 Presidential campaign of left-wing Democrat Gary Hart. Hart started his career in politics as the national campaign manager for radical left-wing George McGovern.
Schundler was deeply disappointed when his left-wing candidate Gary Hart failed in his bid to become President of the United States. Schundler very much wanted to see President Ronald Reagan defeated for re-election in 1984.
Schundler tried to create a niche for himself in the New Jersey Democrat party. However, he discovered that the Democrat Party in left-wing Hudson County, New Jersey was already crowded with ambitious Democrats who had worked for decades developing relationships with party leaders and party activists. Schundler saw that he would be at a disadvantage as a newcomer to the Democrat Party in Hudson County, and that the powerful Hudson County Democrat organization supported candidates according to seniority - something which Schundler lacked.
So Schundler decided to join the Hudson County Republican Party in the 1990s. Since Hudson County is overwhelmingly Democrat, the anemic Republican Party had difficulty finding candidates to run for office and was therefore willing to welcome Schundler.
Don't be fooled by what Schundlers says!