ALBANY — The leader of the state Senate Democrats, Malcolm Smith, could become a victim of his party’s success.

Mr. Smith, a representative of Queens who was picked by his colleagues last year to succeed David Paterson as minority leader, is in position to become one of the three most powerful state officials. His party is two seats away from taking over the Senate for the first time in more than 40 years and is hoping to clinch the majority next year with the help of Governor Spitzer.

Senate Democratic sources, however, say a Democratic victory could upset the dynamic that brought Mr. Smith to power and set off a struggle for the majority leader post. For rivals and allies of Mr. Smith, the chance to become the next Joseph Bruno (the current majority leader) might be too tempting to pass up.

Such a battle would not be unprecedented. In 1965, when Democrats briefly gained control of the Senate, a battle broke out over the majority leader post. Senator Joseph Zaretzki, who was the minority leader and was backed by Mayor Wagner, was challenged by Jack Bronston, who lost his bid after Governor Rockefeller sided with Zaretzki and Wagner.

If there’s a competition for Mr. Smith’s job next year, Mr. Spitzer would likely be the kingmaker.

Sources say the leading contender for the job is Jeffrey Klein, a Bronx representative close to the county’s Democratic leadership who has made his mark in Albany as a prolific fund raiser and savvy legislator adept at turning bills into headlines.

Mr. Klein, who was a top contender for the minority leader post last year before throwing his support behind Mr. Smith, said in an interview that he fully supports Mr. Smith and is not interested in the majority leader job. Mr. Smith, after taking over the conference, appointed Mr. Klein his deputy leader.

After a long period of stalemate, Mr. Smith won the job last year after gaining support from Mr. Paterson, Mr. Spitzer’s lieutenant governor, and picking up a vote from Shirley Huntley, whose candidacy against incumbent Ada Smith was supported by Mr. Smith. Mr. Smith, who is close to former Rep. Floyd Flake, became the second consecutive African-American to lead the Democrats.

Mr. Smith’s colleagues describe him as a likable politician whose most significant political decision — forming an alliance with the governor — was wise. A number of Democratic senators and Senate aides say, however, that Mr. Smith has made several missteps.

In particular, they question Mr. Smith’s decision to speak openly about his plans to lure various Senate Republicans to switch parties. No Republican this year has flipped, making Mr. Smith’s threat seem premature and empty.

Mr. Smith was also criticized for initially agreeing to support a legislative pay raise bill proposed by Senate Republicans. The move infuriated both the governor and some of Mr. Smith’s colleagues, particularly the marginal members, who did not want their names to be attached to the bill.

Under orders from Mr. Spitzer, Mr. Smith ended up opposing and ultimately derailing the pay raise measure, angering Assembly Democrats and Senate Republicans who lost their ability to override the governor.

Mr. Klein said his conference members are supportive of their close relationship with the governor but are concerned that Mr. Spitzer has not properly rewarded them for their loyalty. “They want the governor to deliver a lot more than he has,” Mr. Klein said.

Senate Democrats have been counting on Mr. Spitzer to deliver on their request for millions of dollars in capital funding for local district projects. The governor, who controls his own pool of capital money, is expected to channel some of the money to Democrats this month.