The upcoming special election to replace Rep. Kirsten Gillibrand (D), who will be sworn in Tuesday as New York’s junior Senator, presents opportunities for Republicans and Democrats — and an infinite amount of political peril.

By all rights, Republicans should be favored to recapture the rural upstate seat that Gillibrand won in a bloody upset in 2006. A win would provide the GOP with a desperately needed sense of momentum following two disastrous election cycles.

But after three special House races last year turned conventional wisdom on its head, leaders of both parties are wary about claiming any kind of early advantage.

“We view this as a potential opportunity,” said Ken Spain, communications director for the National Republican Congressional Committee.

Ryan Rudominer, a spokesman for the Democratic Congressional Campaign Committee, was equally circumspect.

“While a special election will be difficult in this traditionally Republican-leaning district, the New York Democrats and the DCCC are working aggressively to keep this district in the Democratic column,” he said.

Part of what’s keeping both national parties on edge is that they don’t know what kind of nominees they’ll wind up with — and they have precious little say in the process. The parties probably won’t decide how much money that they are going to invest in the race until they know who the candidates are.

Gov. David Paterson (D) is expected later this week to formally call a special election, and it would come 30 to 40 days after he officially makes the declaration. But there will be no primaries: The party chairmen from the 10 counties in the sprawling district get to select their nominees in a weighted vote based on population.

This morning in Albany, the 10 GOP chairmen from the 20th district are scheduled to meet — but whether they’re prepared to anoint someone or will merely discuss procedure and the pros and cons of prospective candidates remains to be seen.

“If there’s an overwhelming sentiment to go one way, there’s no sense in wasting time,” said Matt Walter, a spokesman for the New York Republican Party.

But several GOP insiders cautioned that the county chairmen are unlikely to have reached a consensus by the time they meet.

Similarly, the 10 Democratic leaders held a 90-minute conference call Sunday night, but Saratoga County Chairman Larry Bulman, representing the biggest county in the 20th district, said Monday that it could be another week or two before the party designates its nominee. All 10 county chairmen released a statement Monday night saying they would accept applications for the House nomination until noon on Wednesday.

For Republicans, whose performance at the Congressional level in New York has been even more bleak than it has been nationally — they went from having 12 Members in the Empire State delegation in 2002 to three Members Tuesday — a special election win would be particularly meaningful.

“This is an open seat in an area that traditionally has leaned Republican,” one national GOP strategist said. “It is the kind of seat Republicans need to make competitive if they want to begin a march back toward respectability in the House.”

Republicans certainly have a top-tier array of highly conventional candidates vying for the nomination. The list of leading contenders includes state Assembly Minority Leader James Tedisco; former Assembly Minority Leader John Faso, who was the GOP nominee for state comptroller in 2002 and for governor in 2006; state Sen. Betty Little; and Richard Wager, a former aide to New York Mayor Michael Bloomberg (I).

Sandy Treadwell, the wealthy former state GOP chairman who was clobbered by Gillibrand last year, has also made his availability known, though he is apparently not campaigning as aggressively as some of the others.

On Saturday, just a day after Paterson named Gillibrand to the Senate, the Saratoga County GOP endorsed Tedisco, giving him about a third of the votes needed to be nominated. Two GOP leaders believe he will be somewhere in the 40 percent range of support when the county chairmen meet Tuesday, but it isn’t clear whether he can get more than 50 percent right away.

“I would say it’s Tedisco’s to lose,” said one Washington, D.C.-based Republican operative with vast experience in New York.

“I don’t think the NRCC should be overconfident, but if it’s Tedisco, he knows how to get press, he’s not going to stop, he knows how to work, and he has good people around him,” the Republican said. “He’s used to doing races without a lot of resources.”

But a veteran Albany-based Democratic operative said Democrats should root for Tedisco to emerge as the nominee because the Assembly GOP has lost seats during his tenure as leader.

“He may be the one bonehead who’s beatable,” the Democrat said. “He’s running a conference that’s constantly losing races.”

If Republicans do not unify around a nominee Tuesday, the wishes of the small but powerful New York Conservative Party, frequently a major player in GOP nominating fights, could become a factor.

Michael Long, the longtime Conservative Party chairman, was traveling Monday and could not be reached for comment. But Shaun Marie Levine, the party’s executive director, said the state party, which gets to designate its nominee, is talking with its county chairmen and is pleased with the Republican field.

“We’re in a lot better condition than the Democrats are,” she said. “They’re really at a loss.”

While the Democrats may be missing well-known frontrunners, they are not at a loss for candidates. According to Bulman, the number of people who have been in touch with county Democratic chairmen about the House race is approaching 30.

With a far bigger and less conventional field of contenders than the Republicans, the Democrats, in a sense, have more potential than the GOP — but they also have a far better chance of seeing their nominee fall flat or implode.

In the days following Gillibrand’s appointment to the Senate, several Democrats were named as possible contenders, including former New York Rangers goalie Mike Richter, who lives in Connecticut but owns a home in upstate New York; state Assemblyman Tim Gordon, a member of the Independence Party who was elected with Democratic support; attorney Carol Schrager; Saratoga Springs Public Safety Commissioner Ron Kim; Coxsackie Town Supervisor Alex Betke; and Bulman.

The potential Democratic field is so large and fluid that a former Albany TV broadcaster, Tracy Egan, has expressed an interest in running and a current local TV news personality, Benita Zahn, is also thinking about making the race.

But two names that had only been in circulation since late Monday were beginning to excite local Democratic leaders: Suzy Ballantyne, who is a top official at the New York AFL-CIO, and Scott Murphy, a venture capitalist and one-time political operative in his home state of Missouri.

Ballantyne, Democrats say, has close ties to Gillibrand and Clinton, and he could raise a tidy sum of money from organized labor. She did not respond to a message left at her office Monday.

Murphy has only lived in the district for three years, but his wife comes from a large and prominent family in the Glens Falls area and he’s the kind of young entrepreneur who could appeal to a wide range of voters. Murphy said he has been driving to each of the county chairmen’s homes in the past two days and that his message of economic growth has been resonating. He said he has just begun raising money and is willing to invest some of his own money into the race, although he declined to say how much.

Bulman said the DCCC so far has made no promises about what it’s willing to spend on the race and will wait to see who is nominated and what that candidate’s potential is.

“They are going to treat our candidate just as they treated Kirsten Gillibrand initially,” he said. “They weren’t with her from day one.”

The D.C.-based Republican strategist with New York experience said he expects both parties to spend liberally because most of the media markets in the district are relatively inexpensive.

“I wouldn’t be overconfident,” the strategist said he is telling Republicans in Washington and New York. “You guys gotta go in there and understand that you’re going to be outspent 2-to-1.”