There’s an unwritten rule for New York Republicans seeking office: To win an election, get the support of the Conservative Party.

With the Empire State’s GOP trying to wrest control of two seats that the Democrats captured in the past cycle in Republican- leaning districts, its candidates already are courting the Conservatives. But some Republicans wonder whether this small but powerful third party, which has staked out ground to the right of the GOP, will force their hopefuls too far away from the center.

Since New York permits cross-endorsements, Republicans who win the support of the Conservatives almost always gain access to both parties’ lines on the general election ballot.

Close races could be on the horizon in the 19th and 20th districts, both of which have upward of 9,000 registered Conservatives, so getting the party’s endorsement seems particularly important to some Republican candidates in those parts of the state.

“It’s obviously something I want very much. It’s something that I’m working hard to earn,” said former state Republican Party Chairman Sandy Treadwell, the leader in fundraising to date among a pack of Republicans aiming to unseat freshman Rep. Kirsten Gillibrand (D) in the 20th district.

The GOP’s fundraising leader in the 19th district is businessman and Federal Thrift Investment Board Chairman Andrew Saul, the favorite of national Republicans to oust freshman Rep. John Hall (D). Saul, like Treadwell, is trying to woo Conservatives.

But whether their courtship will pay off remains to be seen, as state Conservative Party Chairman Mike Long, a 67-year-old liquor store owner from Brooklyn who carries the reputation of a tried-and-true hardliner, said he is still watching and waiting.

While the Conservatives almost always support the GOP candidate and rarely run their own in House races, this could be because Republican leaders consider the preferences of Long’s party when they decide who to support in their primaries. Those who are fiscally conservative and oppose abortion rights are more likely to win Conservative approval.

Michael Edelman, a New York Republican consultant and commentator, said the net result is that the GOP often hamstrings the campaigns of moderates and nominates candidates who are too far to the right for swing districts such as the 19th and 20th, even though both districts were long represented by Republicans with moderate-to-conservative voting records.

“The problem in New York is that the Conservative Party has entirely too much to say about who the Republican Party runs,” he said. “Any candidate that has to lock step with the Conservative social right-wing agenda in order to get the nomination … is not going to beat the [Democratic] incumbent.”

But Long said his party is simply trying to support candidates who distinguish themselves from the Democrats.

“I don’t think the way to win … is to move to the left,” he said.

The real test of Long’s convictions may come when his party has to decide about Treadwell and Saul. Both have been touting their fiscal conservatism, but they also support abortion rights.

Long is staunchly anti-abortion, but he said whether Treadwell and Saul will win the Conservative endorsements almost entirely depends on if they can convince the party’s grass-roots leaders to back them. In the 19th and 20th districts, he said, some local Conservative leaders have jumped from the party platform and supported abortion rights.

“I’m sure I have differences with both of them, but I’m not the only voice in this selection process,” he said.

The Conservatives likely will not make their endorsements public until next summer — just weeks before the September GOP primaries — but their opinions may circulate among Empire State political insiders before then.

In the meantime, Treadwell and Saul have been reaching out to Long and to Conservatives in their districts.

Both were present at Long’s annual Conservative Party dinner in New York last week that featured former Speaker Newt Gingrich (R-Ga.) as the keynote attraction, and both also have promised to hold the line on taxes. Treadwell made this pledge to 6,800 Conservative households in a letter postmarked earlier this month.

While Long said attendance at the dinner does not guarantee support, their presence was encouraging to him because it showed they are interested in connecting with his party. “My hope is that those who are trying to seek the Conservative Party endorsement would come to dinners like that,” he said.

Other factors also will help determine whether Treadwell and Saul win the Conservatives’ blessings.

In the 20th district, Treadwell’s friendship with Long, which dates back several years, could bode well for his candidacy.

Saul is not as close to Long, and former Republican Rep. Joe DioGuardi has not ruled out running in the 19th.

While DioGuardi has not polled well in his recent campaigns, the Conservatives have supported him even when he hasn’t had GOP backing, endorsing him over Republican Sue Kelly in 1994 and 1996. Kelly won both elections and hung onto her seat until losing to Hall in November.

In a state where Democrats hold a 23-6 edge in the Congressional delegation, Hall and Gillibrand hold two of the most vulnerable seats, with Hall possibly on the weakest footing.

After winning by less than 6,000 votes, Hall fell behind Saul, if only by a hair, in second-quarter fundraising. While he still has around twice as much cash on hand, Hall raised $420,000 compared with $423,000 by Saul during the period from April 1 to June 30.

Gillibrand, a talented fundraiser, brought in $717,000 during this time period to dwarf Treadwell, her closest competitor, who raised $340,000. Behind him was Richard Wager (R), an aide to New York Mayor Michael Bloomberg (I) who brought in $180,000.

Gillibrand is a member of the Blue Dog Coalition, a group of fiscally conservative Democrats, which should serve her well in her upstate district.

Still, Hall does have a comparative demographic advantage. Enrolled Republicans outnumber Democrats by only about 13,000 in his district, while the number for Gillibrand is close to 80,000. Both districts supported Sen. Hillary Rodham Clinton (D) and Gov. Eliot Spitzer (D) in 2006, however.

Conservative numbers are relatively high in both districts, with the 19th having the fourth-largest party enrollment in the state as of April and the 20th maintaining the sixth-largest.

Even so, Conservative pull is weaker in House races than it is in statewide contests. While Long said that no Republican in New York has won a statewide race since 1974 without Conservative support, Kelly and former Reps. Benjamin Gilman and Sherwood Boehlert are among the Republicans who have won House elections without the backing of Long’s party.

Also, the Conservatives have shown some moderation at the district level. After supporting DioGuardi in 1994 and ’96, they offered Kelly, an abortion-rights supporter, their line in subsequent elections.

“I’d prefer the candidates to be pro-life, but we’re not a single-issue party,” Long said.

Edelman said he hopes the Conservatives keep that in mind, because having them back away from moderate candidates could fracture the GOP and increase the chances of the Democrats holding onto the 19th and 20th districts.

“Only a centrist is going to win any of these Congressional or national elections,” he said.