GARDEN CITY, N.Y., March 29— He was, in a way, the best friend Nassau County Democrats ever had -- a convenient way to attach the county's fiscal morass to Republican excess and an apparent guarantee of a divided Republican Party.

But now that the Republican Nassau County executive, Thomas S. Gulotta, has announced he will not run for re-election this year, the two Democrats seeking his job suddenly find themselves competing in a changed environment -- one with no convenient bogeyman and the possibility of a united Republican Party.

How well they adjust and whether they will be able to make it through a primary without tearing each other to pieces could determine whether they can take advantage of the Democrats' best chance in decades to capture the county executive's seat.

''It's ours to lose, and we'll lose it if we don't stand the high ground,'' said Larry Aaronson, the chairman of the Nassau Democratic County Committee. Mr. Aaronson has been laboring to preserve party unity since he was elected chairman in January. For a year and a half, Mayor Thomas R. Suozzi, a Democrat of Glen Cove, has been making the rounds of civic groups and raising money for his bid to become county executive. Then, in January he was joined in the race by State Assemblyman Thomas P. DiNapoli, who was credited during his year and a half as party chairman with leading the party to notable victories by helping the Democrats win control of the County Legislature for the first time in 80 years.

Right now Mr. Suozzi has the edge in fund-raising, with a war chest that he puts at $1.1 million, compared with the $600,000 raised so far by Mr. DiNapoli. But Mr. DiNapoli has the edge in endorsements, winning the backing of State Comptroller H. Carl McCall, Attorney General Eliot L. Spitzer, Assembly Speaker Sheldon Silver, Unites States Representative Gary L. Ackerman, 6 of the 10 Democrats on the County Legislature, and several unions and important local Democratic clubs.

Democrats are trying to accentuate the positive -- that they have two strong candidates running, while the Republicans have yet to find one -- and are hoping that the two Toms refrain from a bitter primary campaign that would lead to defeat by whoever becomes the Republican candidate.

So far both candidates are pledging to run positive campaigns.

Mr. Suozzi, 38, is running on his record as the four-term mayor of Glen Cove, highlighting the city's improved financial outlook, the revitalization of its downtown and waterfront, the closing of an incinerator and the cleanup of polluted lands.

''I have been a manager,'' Mr. Suozzi said. ''I have gotten things done.''

Mr. DiNapoli, 47, is running on his Assembly record. He helped create the Nassau Interim Finance Authority to oversee the county's finances, brought Nassau $105 million in much-needed aid and worked with Republican lawmakers to restore financing to Long Island Bus.

Mr. DiNapoli is also running on his record as Democratic chairman; he inherited a divided party and steered it to victories.

''I have a proven ability to work with others, sometimes even across party lines, to get things done,'' Mr. DiNapoli said.

But with neither candidate able to articulate a significant policy difference with the other, a few tremors have been inevitable.

Mr. DiNapoli's supporters paint Mr. Suozzi as too confrontational and inexperienced to run the county. Mr. Suozzi's supporters paint Mr. DiNapoli as lacking in executive experience and tied to the machine.

Last week, the inevitable debate over debating began. Mr. Suozzi challenged Mr. DiNapoli to a series of 10 debates, which aides to Mr. DiNapoli called the tactic of an underdog. Aides to Mr. Suozzi, meanwhile, suggested that Mr. DiNapoli was afraid to commit.

The candidates themselves have tried to be more circumspect.

Mr. Suozzi did not make too much of Mr. DiNapoli's endorsements. ''All those endorsements he has -- that's like bringing a law degree to a fistfight,'' he said. ''It looks good, but it's not what wins the day.''

And Mr. DiNapoli sought to project an aura of unstoppable momentum. ''My personal view is that the primary is going to be the easy part,'' he said. ''The hard part is having the resources to take on the Republicans in the fall.''

Howard A. Scarrow, a professor of political science at the State University at Stony Brook said how the race would unfold was not clear.

''Is it going to be a gentleman's contest, 'Vote for us, not the Republicans,' or is it going to be, 'This other guy is no good, and I'm better'?'' he asked. ''They have such a wonderful chance to get in -- if they don't kill each other.''

Democrats are watching too, hoping that the campaign does not expose old fault lines.

''Given our history, which is decades of division, there is always a fear that we revert back to our natural state,'' said Bruce Nyman, a longtime Democrat who served on the old Board of Supervisors.

Photos: Many back Assemblyman Thomas P. DiNapoli for county executive. (David Jennings for The New York Times); Thomas R. Suozzi is highlighting his record as mayor of Glen Cove. (Kevin P. Coughlin for The New York Times)

POLITICAL MEMO - For Suozzi, the Signposts Point to Albany ...

Call it the rubout at the Racing Palace.

Former Nassau OTB president Larry Aaronson got politically whacked last

week on the third-floor mezzanine usually reserved for high rollers in the

$14-million betting emporium he created, and which nets the agency much of its

profits.

Aaronson's ouster came at the hands of two of three OTB board members, one

a campaign photographer for County Executive Thomas Suozzi, the other a

bookkeeper and bus dispatcher for Nassau Democratic leader Jay Jacobs'

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business. Neither gave a reason for Aaronson's dismissal from the $300-million

agency, nor did they have a resume for his replacement, Dino Amoroso, chief

aide to Brooklyn District Attorney Charles Hynes.

Afterward, Aaronson blamed his firing on politics, specifically Suozzi's

unstated gubernatorial ambitions and the need to bring Nassau's most Democratic

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town, North Hempstead, in line for the county executive.

"At the very least, they are operating a cult of intimidation," said

Aaronson, an ally of Assemb. Thomas DiNapoli (D-Thomaston), who wants to be the

running mate of gubernatorial front-runner Attorney General Eliot Spitzer.

Jacobs tried to put a reform spin on the ouster: "We are removing a person

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who is a former Democratic leader and putting in someone who has been a

non-political prosecutor and a proven manager. In what perversion of logic are

we making a political move?"

However, legislative Presiding Officer Judy Jacobs (D-Woodbury) said the

move "sent shock waves." She added: "But when the smokes clears, it's all

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politics 101."

She also doesn't see how the move helps Suozzi. "I don't see how this helps

make friends," she said.

But Legis. Peter Schmitt (R-Massapequa) said the move shows Suozzi "is

planning to run his gubernatorial campaign with taxpayers' dollars."

Party leader Jacobs would not specify what Aaronson did wrong, saying only,

"When you start to run a shop like you own it, it's a problem." In the past

year, Aaronson got the board to raise his pay more than $30,000, to $198,500,

and earlier got a severance package that will now pay him a year's salary.

But party sources said Jay Jacobs also was upset that Aaronson was too cozy

with Republican holdovers who worked for opponents of Suozzi and Legis. David

Mejias (D-Farmingdale). They also said Jacobs felt the OTB boss worked behind

the scenes to back losing Democratic primary challenger Rocco Iannarelli for

county clerk and hosted a soiree for DiNapoli supporters at the Race Palace

without informing him. "Boy, are they reaching," Aaronson said later.

Aaronson backers privately fear the ouster will lead to further purges,

making OTB a swap shop where Suozzi could trade support for jobs and create a

repository for campaign operatives. They said Amoroso's appointment is an

attempt to win allies in Brooklyn.

However, Jay Jacobs said he has no plans for wholesale firings and

dismissed any political motives for hiring Amoroso, noting that Hynes just

prosecuted former Brooklyn Democratic leader Clarence Norman and has few ties

to the party organization.

But such worries are not lost on Democratic lawmakers still smarting over

misdeeds of former Suozzi aide Peter Sylver and Parks Department appointees who

submitted bogus time sheets.

OTB board chairman Christopher Wright, an Aaronson ally who resigned in

protest, said county lawmakers should consider overhauling the whole board the

way state lawmakers originally intended - with two board members from the party

that controls the legislature and one from the minority party. It is a dictum

both parties have skirted for decades.

County lawmakers meet today, but chances of a board overhaul are a

long-shot because the presiding officer would have to agree to put the issue on

the agenda or it would require 13 votes to pass as an emergency resolution.

"I don't think anyone is trying to create World War III over this," Judy

Jacobs said. "We shouldn't be adding to the flames."

However, Schmitt said, "I'll certainly leave my door open if anyone wants

to remedy the problem."

query.nytimes.com/gst/fullpage.html?res...

Dec 18, 2005 - TALK of Thomas R. Suozzi's running for governor began even before he took ... was fired as head of the Nassau Off-Track Betting Corporation. Mr. Aaronson, a close ally of Thomas P. DiNapoli, the assemblyman Mr. Suozzi ...