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SILVER SPRING, Md. — Citing his long legislative record and improving performance in opinion polls, Senator Bernie Sanders of Vermont told leaders of the A.F.L.-C.I.O. gathered here on Wednesday that he was best equipped to advance the rights and benefits of organized labor.

Although he did not mention his rivals by name, Mr. Sanders, who was one of several candidates to address the organization’s executive council, said he told the group that no one had as clear a regard for the labor movement as he did

“I have been in the House and Senate for 25 years. I am not aware that there is anybody in the House and Senate who has a stronger voting record for the A.F.L.-C.I.O. during that period — 98 percent,” Mr. Sanders said he told the executive council, adding in jest, “As I recall, I have been right on the other 2 percent.”

Speaking with reporters, Mr. Sanders said that during his allotted time he stressed his early and vocal opposition to the Trans-Pacific Partnership, which the A.F.L.-C.I.O. worked to defeat, and the deregulation of the financial services industry. He also said he mentioned legislation that he plans to introduce that would raise the national minimum wage to $15 an hour.

Mike Huckabee, a Republican, and Martin O’Malley, a Democrat, also addressed the group. Hillary Rodham Clinton and former Senator Jim Webb of Virginia will appear on Thursday.

Mr. Sanders, who identifies as a democratic socialist, has seen early signs of support from members of the labor movement and was warmly welcomed, he said. Still, members of the executive council cautioned that they carefully consider each candidate’s electability when determining an endorsement, a potential strike against Mr. Sanders, who trails Mrs. Clinton in polls.

Mr. Sanders told reporters that he referenced new polling data from CNN that shows him comparing favorably in head-to-head matchups with several Republican candidates to demonstrate to the council that he is not only competitive but also electable.

“Can Bernie Sanders win? Well, we know that CNN is an infallible organization, don’t we? So they have told us that yes, I can win,” he said.

The American Federation of Teachers, an affiliate of the A.F.L.-C.IO. that has already endorsed Mrs. Clinton, is run by Randi Weingarten, a longtime ally. Ms. Weingarten said on Wednesday that she was less confident that Mr. Sanders could win the presidency, even if she deeply respected his work.

“This is someone who has spent 25 years fighting to change the balance, just like we have fought to change the balance,” she said. “But what we need to do is win in changing that balance, not just fight. And so our union believes that Hillary Clinton is the one who is going to be able to do that.”

Mrs. Clinton will most likely be greeted here with questions about her stances on the Trans-Pacific Partnership and the $15 minimum wage, issues on which she has not taken decisive positions.

Mr. O’Malley, a former governor of Maryland, preceded Mr. Sanders on Wednesday. According to interviews with several people in the room, Mr. O’Malley told the council members, “You won’t see Larry Summers or Robert Rubin in my cabinet,” referring to two members of President Bill Clinton’s administration who clashed with labor leaders.

The remark received loud applause, the people said.

Still, Mr. O’Malley said he was realistic about his chances of winning its endorsement.

“I am going to work very hard to get as many endorsements as I can, but I recognize that I’m a challenger, man,” he said. “I know it’s a fine line between delusion and imagination when one runs for president with 1 percent name recognition.”