That leaves one candidate: Sarah Palin. She has been sphinx-like about her intentions. If she intends to run, she has financial incentive to delay announcing, because she can keep her contract with Fox News longer. But the same could have been said for Mike Huckabee, who announced his intention not to run earlier this month. And Palin's potential campaign has arguably been wounded by making people think she will not run, since her support then goes to other Tea Party favorites. That damage outweighs the benefit of a few months of paychecks from Fox, though she will still get a bounce if/when she declares her candidacy.
If Palin does not intend to run, she can theoretically put off making an announcement until whenever she feels like it. There are no real drawbacks. Thus, the more time passes before an announcement, the more likely the announcement will be that Palin is not running.
Meanwhile, Bachmann eagerly awaits Palin's decision. The longer Palin waits, the more it harms Bachmann. She, too, will get a bounce if/when she announces she's running. But in the meantime, the Tea Party will be looking at other candidates. One candidate in particular stands to benefit: Herman Cain.
Cain will certainly rely on the Tea Party to gain steam for his candidacy. He has low perceived electability, just as Bachmann and Palin do. History shows that most Republican primary voters care a great deal about electability. But some do not, especially voters who identify more as "Tea Party" than Republican. They want someone who can inspire them with fiery rhetoric. And they'd rather have a candidate with little or no political experience than one who disagrees with them on some issues.
Bachmann, Cain, and Palin will compete for these voters. As long as Bachmann is stuck waiting on the sidelines, they will flock to the previously unknown Cain. There's no question that Bachmann would have preferred to participate in the May 5th debate. She did not attend, and Cain used the event to his advantage. Bachmann will not want the same thing to happen at the June 13th debate.
Ultimately, all of this benefits the "electable" candidates--particularly Tim Pawlenty, who will focus on Iowa. It increases Cain's strength, spliting the vote that might otherwise be united behind Bachmann or Palin. It also increases the probability that a frustrated Bachmann might jump into the race only to find that Palin is running, splitting the vote further.