I would assume he would have to get elected to the House first-—but I really don’t know what the rules are.
Article I, Section 2 of the U.S. Constitution states, “The House of Representatives shall chuse their Speaker and other Officers.”
Although the Constitution does not require the Speaker to be a Member of the House, all Speakers have been Members.
When a Congress convenes for the first time, each major party conference or caucus nominates a candidate for Speaker. Members customarily elect the Speaker by roll call vote. A Member usually votes for the candidate from his or her own party conference or caucus but can vote for anyone, whether that person has been nominated or not.
To be elected, a candidate must receive an absolute majority of the votes cast—which may be less than a majority of the full House because of vacancies, absentee Members, or Members who vote “present.” If no candidate receives the majority of votes, the roll call is repeated until a majority is reached and the Speaker is elected.
http://clerk.house.gov/member_info/memberfaq.aspx
Levin's chances of getting elected as Speaker by GOPe congresscritters is highly unlikely. We know he wouldn't get even 1 vote from the opposite side of the aisle. Matter of fact with numerous Republicans running there is a real possibility that a Democrat may become the successor to John Bonehead Boehner.