ANCHORAGE, Alaska (Reuters) - Five Republican state legislators filed a lawsuit in Alaska state court on Tuesday seeking to block Democrats from investigating whether vice-presidential candidate Gov. Sarah Palin abused her power in firing a state trooper feuding with her family.

Republican vice-presidential nominee and Alaska Governor Sarah Palin pauses during her speech in Golden, Colorado September 15, 2008. REUTERS/Rick Wilking

The lawsuit claims the probe into Palin’s July firing of Public Safety Commissioner Walt Monegan is unconstitutional and politically tainted because it is being managed by Democrats trying to undermine Republican presidential candidate John McCain and Palin, his running mate.

Monegan contends he was dismissed because he failed to fire a state trooper who had been involved in a contentious divorce from Palin’s sister. The investigation was authorized unanimously in July by a bipartisan legislative committee.

Palin, through McCain campaign officials, contends that Monegan was fired for insubordination.

If the investigation is not halted, the attorney representing the five lawmakers said, at the least the two Democrats and Obama supporters on the committee and special investigator Steve Branchflower should be removed from the case.

Branchflower, a former state prosecutor, would have a conflict of interest, the suit argues, because he has worked with Monegan when he was a police chief in Anchorage. The suit calls for the investigation to be delayed until at least after the November election.

“The only reason to complete this investigation before November 4 is to try to impact the outcome of the election,” said Kevin Clarkson, an attorney representing the lawmakers.

An attorney who pursued a similar case 30 years ago predicted the lawsuit will be unsuccessful.

“If there’s an issue about who should be in charge, the court’s not going to get involved. It’s a political question. It’s not a legal question,” said Doug Pope, who argued unsuccessfully on behalf of a former state House speaker who was ousted in a 1970s legislative coup.

The legislature has the right to investigate the executive branch at any time, so the argument that the body lacks authority is “a red herring,” according to Pope.