The preferred scenario is that Ming leads the LibDems to a poor showing in the General Election and falls on his sword to be succeeded by an Orange booker with whom Cameron can do business. The risk is he limps into coalition with Gordon. Don’t expect any concerted Tory attacks on Ming in the near term, the last thing they want is him replaced.
UPDATE : To clarify, the above graph is derived from the number of respondents positively disposed towards Ming minus those negative towards Ming. He managed a positive rating only immediately after becoming leader.