Mary Beth Buchanan's campaign put out a mysterious news release late this afternoon saying she will make a "significant campaign announcement" tomorrow morning off Grant Street.

Our first thought was that the former U.S. Attorney might be dropping out of the race, and she would not deny that when we called her. "You'll have to come and hear what I say tomorrow," she said.

But sources close to the campaign poured cold water on that theory. They said she was not dropping out, and is more likely to throw bombs at GOP primary opponent Keith Rothfus, who has bested her in fundraising and run a surprisingly robust campaign. And being mysterious about her intentions is more likely to get her news coverage than yet another press release saying "Come hear Candidate X attack Candidate Y!"

The news conference is outside the county office building, home of the Allegheny County elections office. Both Buchanan, of Fox Chapel, and Rothfus, of Edgeworth, are county residents.

Here's the full news release:

MARY BETH BUCHANAN PRESS ANNOUCEMENT

WHO:      Mary Beth Buchanan

Candidate for Congress

WHAT:    Significant Campaign Announcement

WHERE:  In front of the Allegheny County Building

542 Forbes Avenue, Pittsburgh, PA

WHEN:    Friday, May 14, 2010

10:15 a.m.