That's what Bill Kristol is telling Fox News:

Sources say former Secretary of State Colin Powell will endorse Barack Obama at the Democratic National Convention, Weekly Standard Editor Bill Kristol told FOX News exclusively on Thursday.

"He may well give a speech at the Democratic convention explaining his endorsement of Obama," Kristol said, citing inside sources.

"This is not an absolute done deal, but these people are very confident that Powell will endorse Obama," Kristol said, adding that he thinks Powell still has "a high respect" for John McCain, Obama's Republican rival.

Powell spokeswoman Peggy Cifrino strongly denied the report.

"There's absolutely no truth to it whatsoever," Cifrino told FOXNews.com. "Colin Powell will not be at either convention. There's absolutely no truth to this."

Whether it will happen, an endorsement by Powell, which Republicans have been bracing for, would certainly hurt McCain. A convention speech, however, would be huge.