Too late—Cantor needs to go down now.
At the same time Cantor has this problem with Romney ~ if he shows up at the head of the ticket in this state (Virginia) he might go down. Romney made himself very unpopular with Conservatives. Cantor can't win without them. Romney can't either.
You might see to that problem of getting Romney off the ticket. That's a far more pressing problem than worrying about Cantor.