WASHINGTON -- The debate will be explosive Thursday when the House of Representatives decides whether to hold Attorney General Eric Holder in contempt of Congress. What happens next could be the opposite – a long, arduous legal struggle over the roles of the executive and legislative branches.

The vote will trigger a new chapter in the long clash between the branches over executive privilege, a battle that’s almost as old as the nation. President Barack Obama is using executive privilege to shield the Justice Department from a subpoena for emails sought by congressional investigators looking into the Operation Fast and Furious gun scandal.

Republicans, like their congressional predecessors since the founding of the nation, aren’t buying it.

“Please clarify the question raised by your assertion of executive privilege,” committee chairman Darrell Issa wrote Monday to Obama. “To what extent were you or your most senior advisers involved in Operation Fast and Furious and the fallout from it?”

White House spokesman Jay Carney insisted Tuesday that the Justice Department still is trying to resolve the dispute.

“And if the Republicans decide not to have this be a purely political issue, we think that this could very easily be resolved,” Carney said. “But it has not been resolved yet, and I think that points to the obvious political nature of this effort by House Republicans.”

Republicans aren’t saying precisely what would happen after the contempt vote.

“We’re still hoping the attorney general will provide the documents necessary for effective oversight,” said Michael Steel, spokesman for House Speaker John Boehner, R-Ohio.

The contempt citation could be sent to Holder’s Justice Department, where the U.S. attorney for the District of Columbia could send the issue to a grand jury.

But the history of these affairs suggests several possible paths for the citation once it leaves Congress: It could get entangled in lengthy legal maneuvering, and it could get resolved outside a courtroom.

Some experts argue the idea that executive privilege is less crucial to presidents nowadays.

Louis Fisher, a retired constitutional law specialist at the Law Library of Congress, noted that Holder has said releasing documents would “inhibit the candor” needed in executive branch deliberations.

“This popular argument is vastly overplayed,” Fisher said. “Nothing prevents executive officials from speaking frankly and honestly to agency heads.”

Such arguments have grown weaker in recent years, Fisher said. “Presidents, including George W. Bush and Barack Obama, work closely with the press to explain how decisions on national security and domestic policy are reached,” he said.

Authors such as Bob Woodward wrote books about Bush and Obama “letting us know what was said in the highly confidential Situation Room about presidential decisions to commit troops to Iraq and Afghanistan,” Fisher noted.

If executive privilege faces a rocky legal road, Congress also faces historic obstacles in making the contempt charge stick.

"A number of obstacles face Congress in any attempt to enforce a subpoena issued against an executive branch official,” said a report last month from the nonpartisan Congressional Research Service. “Efforts to punish an executive branch official for non-compliance with a subpoena through criminal contempt will likely prove unavailing in many, if not most, circumstances."