Updated 8:49 p.m. |  The White House is asserting immunity for top political adviser David Simas in defiance of a subpoena from House Oversight and Government Reform Chairman Darrell Issa.  

In a letter from White House Counsel W. Neil Eggleston, the White House asserted Congress does not have the power to compel Simas to testify, in a showdown between two of the three branches of government.  

Eggleston cited a new legal opinion from the Office of Legal Counsel in the Department of Justice and past precedent of presidents asserting immunity for their top advisers from congressional subpoena.  

“The Executive Branch’s longstanding position, reaffirmed by numerous Administrations of both political parties, is that the President’s immediate advisers are absolutely immune from the congressional testimonial process,” the OLC wrote. “This immunity is rooted in the constitutional separation of powers, and in the immunity of the President himself from congressional compulsion to testify.”  

The OLC cited precedents going back to Presidents Harry Truman and Richard Nixon of asserting executive privilege against testimony. And bother the OLC and Eggleston said Issa had not shown why, exactly, he needed Simas to testify and what questions, exactly, he needed to answer.  

The feud has been brewing for months over the new political strategy office headed by Simas , culminating in a lengthy staff briefing today that Issa said failed to answer all of his questions.  

Simas is director of the remade Office of Political Strategy and Outreach, which the White House contends complies with the Hatch Act limiting the political activities of civil servants.  

But Issa isn’t convinced.  

“The Clinton White House, Bush White House, and other administrations before them have all faced congressional oversight of political activity supported by taxpayer funds,” Issa wrote in a letter to Eggleston earlier Tuesday. “Under this Administration, like previous Administrations, members of President Obama’s cabinet have committed violations of the Hatch Act, which draws a line between campaign and official business.” Issa said earlier Tuesday he expects Simas to honor the subpoena and testify Wednesday.  

“I believe his on-the-record testimony will provide valuable insight into White House efforts to ensure appropriate use of taxpayer funds,” Issa said.  

The letter to Eggleston said that White House staff “declined a request to discuss compliance with the Committee’s document requests” or to describe who was involved in the decision to reopen the political office.  

Ranking Democrat Elijah Cummings ripped Issa.  

“There is no evidence whatsoever to suggest that Mr. Simas or anyone on his staff did anything wrong,” the Maryland Democrat said in a statement. “Today’s briefing from the White House was detailed and thorough, and Committee staff were able to ask all the questions they had. There seems to be no reason to continue this ridiculous confrontation other than to manufacture false controversy as Chairman Issa’s tenure comes to an end.”  

Democrats said nine Issa staffers attended the briefing from White House staffers.  

“The new Office does not raise funds for political candidates, does not schedule travel for Cabinet Secretaries, and does not engage in the types of political ‘boiler-room’ activities that characterized the previous Administration’s Office of Political Affairs,” the Democratic release said. The Democrats said Republican and Democratic staff were able to ask all of the questions they had.  

“At the conclusion of the briefing, the Republican staffer leading the meeting thanked the White House and said, ‘That’s all the questions I have,'” according to the Democrats’ account.  

A Democratic source knocked Issa for failing to show at the meeting.  

“Guess who didn’t even bother to show-up? One guess. Correct, no Issa,” a Democratic source said.  

The Democratic source said staff briefed Issa’s staff for an hour and 15 minutes and answered every question — 45 in all — until they stopped.  

“I do think it’s fairly remarkable, that if Issa wants to be seen as genuinely caring about the issue (and not just cameras), that he didn’t even bother to attend. I would love to know what his staff says he was doing instead,” the source said.  

Issa spokeswoman Becca Glover Watkins said that the offer had been presented as an offer to brief Issa’s staff — an offer that Issa accepted on Friday.  

Simas didn’t attend the meeting either.  

Issa earlier refused to drop his subpoena of Simas  on Monday after a plea from Eggleston, who warned that the subpoena threatened to impinge on the Executive Branch’s prerogatives. In Issa’s letter Friday to the White House, the California Republican offered to reconsider his subpoena if the briefing answered all of his questions.