With congestion pricing, a signature initiative of Mayor Bloomberg’s second term, dead in Albany, the term-limited leader may increasingly resemble a lame duck as he heads into the final stretch of his tenure at City Hall.

The demise of congestion pricing deals a significant blow to Mr. Bloomberg’s agenda and marks his second major initiative to go down to a whimpering defeat in Albany, leaving some political observers to speculate that he will have a tough time proposing and pushing through another plan on a similar scale before he leaves office.

A former deputy mayor under Mayor Giuliani who has battled the Bloomberg administration in court, Randy Mastro, warned that the later the mayor gets into his second term, “the tougher the political lift becomes.”

“His administration is having to grapple with an economic crisis that threatens our local economy, a changing climate in Albany that is proving to be particularly challenging for the city, and a perception that he is at the end of his term and a lame duck when in reality he has almost two years to go,” Mr. Mastro said. “Those are all heavy albatrosses to bear in a second mayoral term.”

In recent weeks, Mr. Bloomberg also has had to contend with the diminishment of his national profile, which had flourished amid feverish speculation that he would run for president as a third-party candidate. The struggling economy and anticipation of deeper budget cuts at City Hall also could hinder Mr. Bloomberg’s ability to fund new initiatives in the coming months.

The mayor indicated yesterday that although congestion pricing was dead after the state Legislature refused to vote on it, he is forging ahead with the rest of his environmental agenda. He said in a statement that he would push the other 126 proposals in his environmental plan to reduce “our carbon footprint and green our City.”

“We will move forward on proposals to plant 1 million trees, introduce hybrid taxis and install green roofs on City buildings. Congestion pricing is just one part of our ambitious agenda,” Mr. Bloomberg said. Rep. Anthony Weiner, a Democratic candidate to replace Mr. Bloomberg who is opposed to congestion pricing, said Mr. Bloomberg is trying solve the big problems, and as long as he keeps doing that “he will be someone to be reckoned with.”

“Usually mayors start to lose their mojo eventually, but Bloomberg seems to not be as susceptible to that because he seems to keep leaning into big problems,” he said. Richard Lipsky, a lobbyist for the Neighborhood Retail Alliance, a coalition of small businesses, said the mayor may have made a tactical error by focusing his energy on “the most contentious item” in his environmental plan, congestion pricing, and suggested that the approach would make it harder to push through the rest of his sustainability agenda.

“He’s got a difficult job ahead in the next 18 months to generate the enthusiasm for the sustainability that winning this fight would have given him,” he said. “It will be a real challenge for the mayor to do that. I’m not sure he’ll be able to achieve it.”

Supporters of Mr. Bloomberg argue that the mayor is the most popular politician in New York State and still commands the national stage even though he has closed the door on a presidential run and is in the second half of his last term.

Mr. Bloomberg is the keynote speaker at Newsweek’s Global Environmental Leadership Conference in Washington today, and is traveling to Chicago later this month to receive an award from the Center for Innovation at the CME Group, an entity formed by the merger of the Chicago Mercantile Exchange and the Chicago Board of Trade.

Mr. Bloomberg’s chief political adviser, Kevin Sheekey, indicated last night that he has no plans to end efforts to promote the mayor as a national leader, even though Mr. Bloomberg has stated definitively that he is not running for president.

Mr. Sheekey, one of the most vocal promoters of the presidential speculation surrounding the mayor, said on NY1 yesterday that Mr. Bloomberg is the one person in America who would be seriously considered as a running mate by both Democratic and Republican candidates.

“And, I’ll say it right now, the person that picks Mike Bloomberg will win the election in November,” Mr. Sheekey said.

A former top aide to Mayor Bloomberg, William Cunningham, disputed the idea that the mayor would see his influence diminish as he nears his last days in office, arguing that the City Charter gives the office of mayor extraordinary power in the life of the city. That power doesn’t change from the day officials are elected to the day they leave.

An American president, he said, is in danger of becoming a lame duck when Congress realizes that the chief executive won’t be around much longer, but mayors are heavily involved in the city’s budget and in the day-to-day management of the city no matter what year in office they are in.

Mayor Koch said he thinks Mr. Bloomberg has a remarkably good team in place, and that it would work until the last day.

“And what they don’t get through, they’ll urge their successor to continue,” he said. “We didn’t hunker down because it was the end of an administration, and I don’t think that Bloomberg will.”