A top aide to House Speaker John A. Boehner (R-Ohio) is departing to serve as spokesman for an association representing thousands of health insurers.

Brendan Buck, who has served as one of Boehner's top spokesmen for more than three years, will depart today to head up communications for America's Health Insurance Plans, which represents thousands of health-care providers.

Buck is a towering, lanky presence in the U.S. Capitol perhaps best known to political reporters nationwide as one of the few voices who speaks on behalf of Boehner and the broader House Republican Conference. He has focused especially on rapid response to comments and policy introduced by President Obama and congressional Democrats.

Buck took a brief leave of absence in 2012 to serve as press secretary to the vice-presidential campaign of Rep. Paul Ryan (R-Wis.). He previously served as spokesman for the Republican Study Committee, the caucus of the most conservative House Republicans, the National Republican Congressional Committee, and as a spokesman for Rep. Tom Price (R-Ga.).

Boehner said in a statement issued Monday morning that Buck was "absolutely critical" to the GOP's campaign to retake House control in 2010. "Then, he took a leading role in our communications shop, holding the White House accountable in the middle of some of the biggest fights this town has seen in quite a while. I’ve appreciated his advice, his energetic advocacy, and his wit every step of the way. Boehnerland will miss him."

AHIP President and CEO Karen Ignagni said Buck's "experience and skill set will allow him to hit the ground running on day one. He's an effective communicator who knows how to tackle complex policy issues and skillfully navigate an ever-changing health care and media environment. We are delighted to welcome him to our team."

Buck will go from working for a Republican leader skeptical of the Affordable Care Act to an organization that has said little critical of the law

AHIP expressed initial skepticism about the ACA but eventually announced support once it included the “individual mandate” -- the requirement that most Americans have health insurance. Beyond guaranteeing insurers additional customers, the mandate gave AHIP confidence that health plans would have workable “risk pools,” needed to keep their rates from rising too fast, because they would gain new healthy customers as well as ones who were sick and eager for coverage because they needed a lot of care.

As the health-care law has been implemented, including since the opening of the new health exchanges last fall, AHIP has quietly pressed the administration for decisions that would be useful to the industry. But, publicly, the group and individual insurers have largely avoided criticizing the law.

Amy Goldstein contributed to this report.