* The GOP 2012 field takes shape: With Mitch Daniels out and Tim Pawenty announcing today, leading GOP operatives are concluding that the 2012 GOP field is largely in place — it’s Mitt Romney, Jon Huntsman, T-Paw, and the incredible shrinking Newt (or is he still even running?). Some GOP operatives are lamenting that there’s no credible social conservative or “pro-growth” economic conservative, and GOP activists will continue to hope for a savior candidate to materialize.

* T-Paw will appeal to conservatives with contrast to Romney: This advance excerpt from his announcement speech suggests he'll cast himself as the real conservative governor, in contrast to a certain former Massachusetts governor whose experiment in health policy laid the groundwork for the tyranny of Obamacare:

“In Washington, Barack Obama has consistently stood for higher taxes, more spending, more government, more powerful special interests, and less individual freedom. In Minnesota, I cut taxes, cut spending, instituted health care choice and performance pay for teachers, reformed our union benefits, and appointed constitutional conservatives to the Supreme Court. That is how you lead a liberal state in a conservative direction.”

Note T-Paw’s claim that he “instituted health care choice,” a swipe at Romney and Romneycare’s now-despised individual mandate.

* Romney versus a pack of underdogs: Relatedly, a dynamic to watch: The question now is whether T-Paw or the other underdogs can establish himself as the leading alternative to Mitt.

* The Dem attack on T-Paw: The DNC is out with a new video that combines what Dems see as his two primary vulnerabilities: His rapid abandonment of once sensible positions on issues like cap and trade in order to make himself acceptable in a GOP primary; and his recent admission that he doesn’t know why he's running for president.

* Liberals will press T-Paw on Medicare: So where is T-Paw on the Paul Ryan proposal? He initially praised the plan before criticizing it, and has dodged questions on whether he supports it.

“Does Pawlenty have the courage to take a stand on ending Medicare?” emails Eddie Vale of ProtectYourCare.org, a sign that Obama’s allies will continue doing all they can to ensure that the battle over Medicare frames the 2012 presidential race at the outset.

* Former NRCC chief says GOP has lost its advantage: This may drive some discussion today: Tom Davis, a former head of the National Republican Congressional Committee, thinks the electoral dynamic that enabled House GOPers to pick up 63 seats last year has played out.

“The tailwind that brought Republicans to the 63 margin is gone,” Davis said. “We are back to a more normal setting.”

* House GOP Medicare plan too hot for Senate Republicans? On Fox yesterday, Mitch McConnell seemed unable to explain why Paul Ryan’s plan isn’t a “voucher” plan, and said the Medicare talks that really matter are the bipartisan deficit talks being led by Veep Joe Biden.

* Scott Brown comes out against Ryan plan: Indeed, after days of hemming and hawing, Senator Scott Brown says he’ll vote No. He agrees with the Dem critique that it would adversely impact seniors and would end Medicare as we know it, a sign that Dems may be winning the political battle to define Ryancare.

Key fact: Brown is up for reelection next year.

* In NY-26, Medicare is the most important issue: Relatedly, the new Siena poll finding that Dem Kathy Hochul has edged into a lead in this nationally watched special election also finds that Medicare is the most important issue determining how people will vote.

* A microcosm of the GOP’s national problems? With the election set for tomorrow, Dems have to be glad that the national press is treating the race as a referendum on whether the national GOP has overreached in the quest for deep spending and entitlements cuts.

* How crazy do you have to act to win 2012 GOP primary? Relatedly, Paul Krugman on how the GOP primary could end up drawing the party ever deeper into economic extremism.

* But will swing state Dems draw hard line against Medicare cuts? Liberal groups are set to release a batch of swing-state polls showing overwhelming oppostion to cutting Medicare, an effort to pressure senators like Claire McCaskill, Jon Tester and Amy Klobuchar to stiffen their spines and take Medicare benefits cuts off the table.

* And no retreat in Obama’s speech to AIPAC: Good read from Philip Weiss on how Obama’s speech yesterday to the Israeli lobby didn’t retreat an inch from the 1967 lines marker he laid down the other day.

Also worth reading: Jeffrey Goldberg, who has done great work on this story, similarly hails Obama’s speech for being “tough on Israeli procrastination.”

What else is happening?