Democratic Senator Evan Bayh's sudden, surprising retirement looks more and more like a very public break between the moderate from Indiana and the more liberal Democrats in Congress and the White House. Bayh, who positions himself as a centrist, has been unflinching in his criticism of both parties. The suddenness of his retirement, and the fact that Bayh remains popular in his Republican-leaning home state, has spurred speculation about a potential 2012 presidential run. Could Bayh run, possibly as a third-party centrist or possibly as a Democratic primary challenger to President Obama?

• The Untarnished Democrat  The Washington Post's Chuck Lane sees a branding possibility. "Quitting the Senate was a no-lose move for the presidentially ambitious Bayh, since he can now crawl away from the political wreckage for a couple of years, plausibly alleging that he tried to steer the party in a different direction -- and then be perfectly positioned to mount a centrist primary challenge to Obama in 2012, depending on circumstances."

• Running as a Centrist 'Outsider'  The Guardian's Michael Tomasky evaluates the prospects. "I say it's a reasonable bet that Bayh doesn't necessarily think his career is over. He's probably still eyeing the White House, and maybe thinking that being out of office -- being, say, a university president back in Indiana -- is a better springboard than a Senate that everyone in America hates." Bayh was "a darling of centrist Democrats, and he was touted as a presidential candidate back in 2006-07 and indeed took some steps toward a run before deciding not to."

• 'Centrists Cannot Win As Insurgents'  So argues conservative blogger Daniel Larison.

Parties tend not to reward shirkers and deserters with promotion. Party politics may be infuriatingly, mind-numbingly tribal much of the time, but that is definitely something one can always rely on it to be. To retire from the field at a time when his party can’t afford to have any more vulnerable seats and then to do so without warning and at virtually the last possible minute before the filing deadline for candidates will mark him for the special loathing of progressive activists and donors for years to come.

• Dems Won't Vote Against Obama  Liberal blogger Matthew Yglesias wonders where Bayh would get votes. "No incumbent president has ever been defeated in a primary," he writes. "On top of that, successful primary challenges to incumbents are invariably driven by base-oriented candidates knocking off incumbents who’ve strayed too far off the reservation. [...] there’s just no sign that Democrats have any problem with Barack Obama."

• Bayh-Bloomberg 2012 Ticket?  Why, asks Sandy Levinson, couldn't Bayh join with New York Mayor Michael Bloomberg, a former Republican turned Obama-backer? "This certainly doesn't sound like a crazy idea to me, given the presumed ambition of both men and the deep pockets of Michael Bloomberg," she writes.
  

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