In December, Pennsylvania Insurance Commissioner Joel Ario went to a Christmas party at the White House.

In March, he sat next to President Obama at a meeting in the White House's Roosevelt Room.

Effective Aug. 30, Ario will leave his post in Harrisburg to take a job in Washington helping Obama develop a key component of the nation's new health-care system.

In a March interview, Ario said he liked the president. "I was certainly impressed with the guy. He's very low-key, a very empathetic listener, and I think quite persuasive."

Ario's job will be in the new federal Office of Consumer Information and Oversight.

"We'll be losing a good regulator," said Insurance Department spokeswoman Melissa Fox.

Ario, appointed by Gov. Rendell in 2007, will be replaced by Robert Pratter, currently executive deputy general counsel.

Pratter, a former partner in the Philadelphia law firm Duane Morris L.L.P. and a University of Pennsylvania Law School graduate, specialized in insurance law. He was general counsel for PMA Capital Corp. before joining the state government in 2008.

Ario was on vacation and could not be reached for comment. He was Oregon's top insurance regulator before coming to Pennsylvania.

Ario made headlines in January 2009 when he forced the state's two largest insurers - Philadelphia's Independence Blue Cross and Pittsburgh's Highmark Inc. - to withdraw their merger proposal.

"We wish Commissioner Ario well as he takes on a new post in the rollout of health-care reform at the national level," said Independence Blue Cross spokeswoman Judimarie Thomas.

In Washington, he will help create health-insurance exchanges in each state that allow individuals and small businesses to shop for health insurance. These marketplaces are to take effect in 2014.

Ario's leadership in an organization of state insurance commissioners put him in contact with Obama and Kathleen Sebelius, U.S. secretary of Health and Human Services. She got to know Ario when she was Kansas' insurance commissioner.

Ario, who also was a consumer advocate, is one of several top state officials to resign this summer as Rendell nears the end of his term.

Contact staff writer Jane M. Von Bergen at 215-854-2769 or jvonbergen@phillynews.com.