ALBANY – The most powerful Democrat in state government, Sheldon Silver, yesterday belittled the political reform effort begun by the Nassau County executive, Thomas Suozzi, while dismissing Mr. Suozzi’s chances of being elected governor.

Mr. Silver said Mr. Suozzi’s political committee, called “Fix Albany,” has barely made a dent in state politics, and that the Democratic gubernatorial candidate has exaggerated the influence his committee has had in getting insurgent state lawmakers elected. Asked about “Fix Albany,” Mr. Silver said, “I don’t think it existed, actually.”

Mr. Silver’s attack on Mr. Suozzi, which came two days after Mr. Suozzi announced that he is seeking the Democratic nomination for governor, underscored the extent to which the county executive has fallen out of favor with the Democratic Party establishment in Albany.

The ability of Mr. Suozzi, 43, to mount a serious challenge against New York’s attorney general, Eliot Spitzer, whom Mr. Silver endorsed more than two years ago, will depend to a large degree on how voters view his outsider status.

The 43-year-old Mr. Suozzi is counting on his self-styled reputation as a rebel Democrat to appeal to voters who want to shake up politics in Albany, and he hasn’t shied away from acknowledging his combative relationship with Mr. Silver. “Shelly Silver doesn’t even see a need to reform Albany,” a spokeswoman for Mr. Suozzi, Kimberly Devlin, told The New York Sun.

Mr. Silver’s bitter attitude toward Mr. Suozzi dates back at least to 2003, when Mr. Suozzi blamed lawmakers for shifting too much of the tax burden on local governments and threatened to oust two lawmakers from his home county – a Democrat in the Assembly and a Republican in the Senate. Mr. Silver, in return, tried to exclude him from the 2004 Democratic National Convention in Boston, and soon after Mr. Suozzi made his threat, a high-powered lobbyist, Patricia Lynch, canceled her contract with Nassau County, ostensibly because of the county executive’s challenge to Mr. Silver.

The Fix Albany political committee, which Mr. Suozzi started to help make good on his threat, has had mixed results. It backed Charles Lavine, a lawyer of Glen Cove who defied expectations by toppling the 12-year incumbent, David Sidikman, in a Democratic Assembly primary and winning the general election.

His committee also contributed $50,000 to the campaign of David Valesky, who beat the Republican incumbent Nancy Larraine Hoffmann by one percentage point in a Senate race in Syracuse. But the committee failed to oust two Republican senators from Nassau that it had targeted, Carl Marcellino and Dean Skelos, the deputy majority leader.

“Valesky and Lavine were just more examples of Tom Suozzi’s reform message defeating Shelly Silver’s status quo candidates,” Ms. Devlin said.

Mr. Silver said yesterday that residents of Glen Cove, where Mr. Suozzi and three other relatives of his have served as mayor, voted overwhelmingly in favor of Mr. Lavine, but residents outside the city gave him much weaker support, suggesting that Mr. Suozzi’s influence does not extend beyond his hometown.

Asked whether Mr. Suozzi could defeat Mr. Spitzer, who is leading by a wide margin in the polls, Mr. Silver said, “I personally don’t think he has a shot.”