From the Des Moines Register:

Republican National Committee member Steve Scheffler e-mailed me this morning to say that he’ll be “lobbying hard” to include Texas Gov. Rick Perry and former Alaska Gov. Sarah Palin on the Iowa Republican Straw Poll ballot.
He also advocates including declared candidates Mitt Romney, Jon Huntsman and Newt Gingrich on the Aug. 13 straw poll ballot. …
Currently, only six candidates are automatically included by virtue of purchasing space for their campaigns at the Ames fundraiser: Michele Bachmann, Herman Cain, Thaddeus McCotter, Tim Pawlenty, Ron Paul and Rick Santorum. Only those six will be allowed to speak at the event.
The Republican Party of Iowa’s state central committee will vote Saturday on the final ballot.

In 2007, John McCain, Rudy Giuliani, and Fred Thompson (none of whom had bought a spot at Ames, and Thompson wasn’t even officially running at that point) were all permitted to be on the Ames Straw Poll ballot.

Ellen Carmichael, spokeswoman for Herman Cain, told Talking Points Memo that “by putting people on the ballot who didn’t pay, [the state party] has the potential to weaken Iowa’s status as the first in the nation caucus.”