Alternate universe? Seriously?
David Palmer was brought in because in season 4, Logan was portrayed as in over his head and needed help to deal with the Presidency suddenly being thrown onto his lap in the middle of a serious (ridiculous) threat. In season 5, he was basically a good guy (now more comfortable in his own skin) doing whatever he could to help Jack... until he suddenly became the bad guy because the writers needed yet another shocking twist for the sake of a twist.
Do you also think seasons 4, 6 and 8 are the best?