Complex sentence: During the 2008 Democratic Presidential Nomination battle he was on of the first to endorse Senator Hillary Clinton, on May 1,2008, however, he decided to switch his allegiance to Senator Barack Obama.
Split into simpler sentences: During the 2008 Democratic Presidential nominating contest he was one of the first to endorse Senator Hillary Clinton. On May 1,2008, however, he decided to switch his allegiance from Clinton to Senator Barack Obama.