Bachmann has been added to the Elephant Watcher roster of candidates. She has been analyzed and her odds of winning the nomination have been calculated. Bachmann's Profile may be found here. Bachmann currently has a 1% chance of winning the nomination. Palin's chances have dropped by 1%.
According to CNN, there will be seven participants at the June 13th debate: The five men who have already officially declared they are running (Cain, Gingrich, Paul, Pawlenty, Romney), the one who has an exploratory committee (Santorum), and Bachmann. CNN's invitations were based on "objective criteria," which they list here. Note that unlike the May 5th debate, candidates were not required to form exploratory committees first. CNN was probably eager to allow Bachmann to attend, since they enjoy reporting gaffes made by the congresswoman.
As Elephant Watcher expected, CNN was eager to trim the field by removing an unimportant candidate, former New Mexico governor Gary Johnson, who had attended the May 5th debate. CNN's criteria were likely chosen with this purpose in mind.
Also of note is the fact that an invitation was offered to Jon Huntsman, Jr., but it was declined. He is apparently still making up his mind whether or not to actually run. His refusal to attend the debate suggests there is a real chance he could decide against it: Huntsman has low name-recognition and could use a boost in visibility.