The strange alliance between Mitt Romney and Ron Paul, where neither attacks the other and Paul savages the conservative credentials of Romney’s challengers, continues with a fresh Paul TV ad on the air in Michigan tearing into Rick Santorum:

What’s more, Paul’s campaign is distributing ‘oppo’ — opposition research — attacking Santorum but not Romney. Which will only compound the negative ads Romney’s Super PAC is pouring into the state to neutralize the latest threat to their candidate’s march to Tampa.