I found this thread late, and didn't read all 5 pages, so this sighting may have already been posted, but my experience was:

End of September 2004, taxiing from the gate at MIA on an AA flight to ATL, I saw Air Force One parked away from the terminal. That evening was the first 2004 debate between Bush and Kerry, and it was being held at University of Miami. So, W was in town to debate.

While waiting to board my plane, I also saw (now former) US Senator Bob Graham (D-FL) come off an arriving plane. Must've been a lot of politicians swarming the airport that day, but I only saw 1.