It is, obviously, perfectly OK for Christians to hold prayer rallies. Just as obviously, Christian prayer rallies will feature Christian speakers, not Muslims or Jews or Buddhists. That's the nature of the beast, and it's hardly unusual for an American politician to attend such events.
But Tim Murphy reports that "The Response," a Houston prayer rally funded by the American Family Association and supported by Texas Gov. Rick Perry, is a wee bit more muscular than that:
With this prayerfest, Perry is associating himself with rather radical folks. The American Family Association's issues director, for instance, has said that gays are "Nazis" and that Muslims should be converted to Christianity. Another organizer, Doug Stringer, has said that 9/11 was God's punishment for the nation's creeping secularism. And then there's Jay Swallow, whose endorsement is trumpeted on The Response's website, and who runs "A Christian Military Training Camp for the purpose of dealing with the occult and territorial enemy strong holds in America" (his description). Consequently, it's not much of a mystery why only one of the nation's other 49 governors has so far accepted Perry's invitation to attend the event (Perry invited all of them)—arch-conservative Sam Brownback of Kansas.
So does this mean that Perry is running for president? Maybe! Tim explains more at the link.