In a must-read for political junkies, Joshua Green at Bloomberg Businessweek reports that Newt Gingrich and Rick Santorum considered joining forces to take down Mitt Romney during the 2012 Republican primary. The discussions to form a "unity ticket" came just before Romney's narrow primary win in Michigan in late February, the point at which Romney's nomination became virtually inevitable despite strong misgivings among the conservative base.

According to Green, the Gingrich and Santorum camps thought that an alliance would have unified conservative opposition to Romney and brought him down. "It would have sent shock waves through the establishment and the Romney campaign," John Brabender, Santorum's chief strategist, told Green.

Alas, it was not to be. The sticking point? Gingrich and Santorum couldn't decide who would be president. Gingrich argued that he had just won the South Carolina primary, a huge victory. He also claimed that he deserved the top spot because he was older. But Santorum's camp, correctly as it turned out, countered that Gingrich's campaign was on a clear glide path to defeat, while Santorum was emerging as Romney's biggest rival. 

The negotiations between the two sides were reportedly dead serious, and the two rivals even discussed the unity ticket face to face. But both wanted to be Batman, viewing the sidekick role of Robin as beneath them.

It's worth reading the whole story, which has colorful quotes from both sides, including Santorum and Gingrich.

Could a Santorum-Gingrich ticket have actually defeated Romney? Sure, the former Massachusetts governor was grappling with a highly vocal, "anyone but Romney" contingent in the Republican Party. But many see the fact that the Santorum-Gingrich deal fell apart as more evidence that Romney was a far superior candidate. "It was obvious throughout the 2012 presidential nominating process that the only way a candidate as flawed as Mitt Romney was going to win was to exploit the foibles of his rivals in the probably the weakest field in living memory," argues Ed Kilgore at Washington Monthly. "This is a good example."