Nevada Secretary of State Ross Miller (D) announced Monday that the special election for Rep. Dean Heller’s (R-Nev.) House seat will be open to all candidates and will not feature party primaries — a result that could benefit both 2010 GOP Senate candidate Sharron Angle and Democrats.

Heller will replace Sen. John Ensign (R-Nev.) after Ensign formally resigns this week, but state special election law isn’t very clear on the process for filling a vacancy in a congressional seat.

Miller weighed in Monday, saying that his interpretation of state law is that there will be no primaries or party nominations in the Sept. 13 special election. His decision may not be the end of it, though. Both Republicans and Democrats have filed lawsuits and more are expected.

The National Republican Congressional Committee is already accusing Miller of choosing his party over the law and suggests the courts will decide the matter.

“This blatantly partisan ruling from Harry Reid’s political machine is only the beginning of what will surely be a long and drawn-out process,” NRCC spokesman Tyler Houlton said.

The state Republican Party issued a similar statement and is threatening to sue.

If Miller’s ruling stands, it should help Angle, who likely would have had difficult time winning the nomination if party leaders has been tasked with choosing the candidate.

She is the best known candidate in the race, having run statewide in 2010 and also for the same seat back in 2006, but recent polling has shown even many Nevada Republicans are disillusioned with her. In a free-for-all race, Angle’s committed base matters hugely since 20 to 25 percent could wind up being the winning number.

(Angle won the 2010 Senate primary wirh 40 percent but might struggle to replicate that showing in a more crowded field and in the wake of her disastrous 2010 general election race against Senate Majority Leader Harry Reid.)

The decision may also be a boon to Democrats, who hope to rally around one candidate while Republican slug it out on their side. That may give Democrats a better shot at winning a seat they have never held, but that President Obama nearly carried in 2008.

Democrats appear to be getting their choice candidate, with Jon Ralston reporting that state Treasurer Kate Marshall will run.

(Update: This post initially misreported that Marshall’s chief of staff told Ralston that she would run.)

On the GOP side, Lt. Gov. Brian Krolicki, state GOP Chairman Mark Amodei, former Navy Cmdr. Kirk Lippold and state Sen. Greg Brower are all either running or considering bids.

One candidate who will not be running is Miller himself, who said the idea of running in a special election and running for reelection shortly thereafter doesn’t appeal to him.