Romney's "wingman" targets Santorum in Michigan: 

Sam Stein spotlights Romney and Paul's peculiar friendship: 

So far this campaign cycle, the two candidates have had an informal alliance, with neither of them ever really threatening the other. Paul memorably declined to join the chorus in criticizing Romney's tenure at Bain Capital. Romney, in return, has heaped praise on Paul's influence over the GOP platform on all facets, save foreign policy. The New York Times reported last week on the friendship that has developed between Romney and Paul, dating back to their 2008 runs for the White House. Now, it appears, Paul is going to help drive down Santorum's climbing poll numbers in Michigan, to Romney's benefit.

Paul Waldman addresses the substance of the ad: 

The attack on Santorum is actually pretty revealing. It all flies by pretty fast, but in there you have that Santorum voted to raise the debt ceiling; "doubled the size of the Department of Education" (because he voted for George W. Bush's No Child Left Behind); supported a big entitled expansion (because he voted for George W. Bush's Medicare prescription drug bill); sent billions of our tax dollars to dictators (because he supported aid to Egypt, the second-largest recipient of US aid after Israel); and gave money to Planned Parenthood (not sure, but I'm guessing it refers to something buried deep in a huge spending bill that he voted for). In other words, here's the essence of the attack: Rick Santorum was a Republican US senator when George W. Bush was president!

Meanwhile, Winning Our Future is back as Sheldon Adelson toys with a $100 million infusion. In the new spot below, the Shelly-Gingrich Super PAC reminisces about the 1990s: 

And pivots, "Only one man in this race stood up to Bill Clinton":

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