Gregory Korte

USA TODAY

WASHINGTON -- President Obama's top political adviser in the White House, David Simas, will defy a subpoena to appear before a House oversight committee Wednesday, setting up a political and legal confrontation over the scope of executive power.

As an immediate adviser to the president, Simas "is immune from congressional compulsion to testify on matters relating to his official duties and will not appear" at Wednesday's hearing, White House Counsel Neil Eggleston said in a letter to Congress Tuesday.

House Oversight and Government Reform Committee Chairman Darrell Issa, R-Calif., had sought to compel Simas to testify about the White House Office of Political Strategy and Outreach, which Obama reestablished in January. Specifically, Issa wants to know what the White House was doing to ensure it complies with civil service laws forbidding executive employees from engaging in political activity.

He said Wednesday's hearing would go on with or without Simas.

Issa said the White House was flouting previous court rulings that said White House officials don't have absolute immunity from testifying. In 2007, the Senate Judiciary Committee subpoenaed White House Counsel Harriet Miers to testify about the controversial firings of U.S. Attorneys. An appeals court upheld the subpoena, but said Miers didn't have to discuss privileged information in response to questions.

"Flouting a federal judge's opinion about our system of checks and balances is yet another attack on our nation's constitution by this president," Issa said in a statement.

The White House disagrees with the Miers decision. In a legal opinion released Tuesday, Assistant Attorney General Karl Thompson said the Justice Department would "adhere to the executive branch's longstanding view that the president's immediate advisers have absolute immunity.from congressional compulsion to testify."

The White House Office of Political Affairs has a checkered history dating back to the Carter Administration, but it was under President George W. Bush that it achieved its greatest notoriety. As a candidate for president in 2007, Barack Obama accused the Bush White House of engaging in a "perpetual campaign." A 2011 report by the Office of Special Counsel, which enforces laws designed to keep campaign politics out of the executive branch, found that the Bush White House used the office to improperly dispatch cabinet secretaries to key congressional districts ahead of the 2006 mid-term elections.

But the Obama White House says its Office of Political Strategy and Outreach is "different office, with a different set of limited responsibilities" than what the Bush White House did.

Eggleston said the Oversight Committee's interest in the poltiical office "lacks any predicate of wrongdoing or misconduct."

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