Perhaps Mitt senses the McCain train irreversibly leaving the station:

In a major boost for McCain, Romney signaled earlier Wednesday that he's not ready to commit to a costly campaign in the states holding primaries and caucuses next week.

Several officials said that on the heels of a defeat in Tuesday's Florida primary, Romney's campaign was not attempting to purchase television advertising time in any of the states on the Super Tuesday calendar.

Instead, the former Massachusetts governor's current plans call for campaigning in California and other primary states, said the officials, who had knowledge of the internal discussions. There would be organizational efforts primarily for caucus states.