She broke the news on Twitter:

Driven by the urgency of creating jobs & protecting #hcr, #wsr, Social Security & Medicare, I am running for Dem Leader.

Not everyone in the caucus will support her, obviously. We already have Heath Shuler thinking he can win a Minority Leader race, Jim Matheson has called on her to step down from leadership, and Oklahoma’s Dan Boren followed suit today. But this represents an extreme minority of the 187 member-plus Democratic caucus. I’d be shocked if she didn’t have the numbers well in hand to lead the caucus again.

Given the alternatives, in my view it’s good news. We’ll see what Steny Hoyer has to say about this.

UPDATE: Keep in mind that for the most part, Pelosi never brought anything up for a vote in the House unless she knew she would succeed. I assume we have the same dynamic here.

UPDATE II: Pelosi has released a letter to colleagues outlining her decision. On the flip.

Over the past several days, I have spoken with many Democratic colleagues about how to continue our fight for to make our country more secure and strengthen the middle class, create jobs, protect Social Security and Medicare, and promote the innovation, technology and education to make America Number One in the world. As always, I am inspired by the fighting spirit of our Democratic Members.

As you know, Democrats have produced historic legislation in the area of health care, veterans’ benefits, women’s rights, Wall Street reform, and cutting taxes for 95 percent of the American people and millions of small businesses. And we have restored fiscal discipline to the Congress by making the deficit-cutting Pay As You Go rules the law of the land.

These accomplishments have begun the difficult work of recovering from the worst economic collapse since the 1930s and, according to independent reviews, prevented our country from plunging into another Great Depression. As a result, numerous congressional experts call this the most productive Congress in a half century. This was only possible because our Members had the courage of their convictions and put the interests of the Country first.

Our work is far from finished. As a result of Tuesday’s election, the role of Democrats in the 112th Congress will change, but our commitment to serving the American people will not. We have no intention of allowing our great achievements to be rolled back. It is my hope that we can work in a bipartisan way to create jobs and strengthen the middle class

Many of our colleagues have called with their recommendations on how to continue our fight for the middle class, and have encouraged me to run for House Democratic Leader. Based on those discussions, and driven by the urgency of protecting health care reform, Wall Street reform, and Social Security and Medicare, I have decided to run.

I am writing to respectfully request your support and I look forward to hearing your views. Please let me know what you are thinking.

Thank you for your leadership and friendship.

best wishes,

Nancy Pelosi