Good for Gardy
If Gardenhire can manage to lead the Twins to a World Series while he's here, then I think there's no question he will have a place as the best manager in team history. If not, he'll probably remain behind TK in my book. Honorable mention has to go to Sam Mele, who guided the team to the 1965 AL Pennant and lost a heartbreaking series to the Dodgers - Mele had a winning percentage of .546 in 5 full seasons and 2 shortened seasons (one when he was hired late in 1961, and one when he was fired in 1967).
One parting note: The Twins have been to the post-season 9 times (not counting the Washington Senators era) - four of those have been under the leadership of Gardenhire. This is admittedly an easier hurdle to jump in the Wild Card era, but the number is pretty amazing nonetheless. Gardenhire doesn't deserve all the credit for that success (Terry Ryan deserves some love, in my opinion, as well), but without a good manager those teams would not have been playoff teams.