Clinton Summons Top Donors, Supporters For Tuesday Speech.

Hillary Clinton has summoned top donors and backers to attend her speech tomorrow night in an unusual move that is being widely interpreted to mean she plans to suspend her campaign and endorse Barack Obama. Obama and Clinton spoke Sunday night and agreed that their staffs should begin negotiations over post-primary activities. In addition to help raising money to pay off some $20 million-plus in debts, Clinton is known to want Obama to help out black officials who endorsed her and are now taking constituent heat, including, in some cases, primary challenges from pro-Obama politicians.

"This has never happened before," one donor said, referring to the personalized request by email to attend the event in New York Tuesday night.

Of course, suspending the campaign does not mean folding the tent and packing it up. Anything could happen if negotiations don't work out between the two camps.

UPDATE: Then again, maybe that trial balloon just popped.

Ken Vogel reports from the Clinton bubble a Clinton spokesman is pushing back on the notion of a concession soon, something even many of her aides and top supporters now expect.

Hillary Clinton will not drop out of the presidential race Tuesday or in several days that follow, the spokesman,Mo Elleithee, said Monday afternoon.

"It's pretty clear that she's not conceding," Elleithee told reporters on Clinton's campaign plane en route from Rapid City, S.D. to Sioux City, Iowa.

Instead, Elleithee said Clinton would be "aggressively courting" superdelegates and "putting together the next phase of the campaign," which he said could include campaign events around the country.

* Report: Clinton campaign advance staff given walking papers