When do politicians rate a TFR?

In an amazing (disgusting, IMHO) display of political hackery (Yep,
that's a word, now) the State of Iowa is being flooded with every
potential presidential candidate, despite the fact that the election
is not until November -- of 2008!

Iowa City in particular has been targeted by Hillary and Obama, to the
point where I wouldn't be surprised if they applied for residency. It
seems like they have been here every other week -- and now the
Republican candidates are following suit.

Having been unpleasantly surprised by a TFR back when John Edwards was
running as a VP candidate (I was on the ground, thankfully, but
couldn't get to my plane, thanks to the SS), we now live in fear of
pop-up TFRs here on a daily basis.

Unfortunately, I have been unable to find any information on precisely
whom is eligible for a TFR. Is this a rule that's written down
anywhere?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"