This article says Clark is staying in.
Democratic presidential candidate Wesley Clark told staffers on Tuesday his campaign would move on to Wisconsin this week as the former NATO commander awaited results in Tennessee and Virginia considered key to his candidacy [...]
Campaign spokesman Jamal Simmons said, "The general has always said he intends to stay in the race through Super Tuesday," the 10-state vote on March 2.
The cancelled fundraiser? I guess he's going to Wisconsin right away and doesn't want to miss a single day of campaigning.
Good news for Kerry, bad news for everyone else.
Update: I added the "maybe" to the tile because the Houston fundraiser seemed to be cancelled after this story was written.
In other words, the article was written in the late morning (as you read it, it seems to include the General's morning schedule). The fundraiser cancellation took place after the noon exit poll reports.
For now, I'll take the Reuter's piece at face value that Clark is staying in, but I wouldn't bet any money on it.