Neera Tanden, one of the Obama administration's top health care reform advisers, is leaving to become chief operating officer at the Center for American Progress (CAP), the liberal Washington think-tank with close ties to the Democratic establishment.

Tanden, a longtime adviser to and confidante of Hillary Clinton, first joined the Obama team when he became the Democratic presidential nominee in the summer of 2008. After serving as Obama's domestic policy director for the general election campaign, she became the senior adviser for health reform at the Department of Health and Human Services.

The timing of the announcement, given the highly uncertain prospects for Obama's reform plan, is sure to raise some questions. But a source close to Tanden says the move has been in the works for months--and that she's leaving now only because she couldn't postpone the departure any longer. Her advocacy for health care reform, a cause she has long championed, will continue.

One reason I believe that to be true is some inside information: In addition to taking the reigns at CAP, Tanden reached an agreement with this magazine's editors to write about policy for tnr.com

Tanden's previous experience includes stints in the Clinton White House and the Democratic Congressional Campaign Committee. She was also a senior policy advisor to Harold Levy, chancellor of the New York City Schools. She is a graduate of UCLA and Yale Law School.

CAP will formally announce Tanden's hiring on Friday.