NEWTON - Joseph P. Kennedy III’s candidacy for office may still be uncertain - but you would never know it, judging from the voters at a Democratic caucus here yesterday.

Kennedy, who is considering a bid for the congressional seat being vacated by Barney Frank, a Democrat, made an appearance at the caucus held at Newton South High School to shake hands and meet potential supporters. Elizabeth Warren, who is challenging Senator Scott Brown, a Republican, in the next election, also came to the caucus, delivering enthusiastic speeches to local Democrats.

Kennedy, the 31-year-old grandson of Robert F. Kennedy, announced last month that he had created an exploratory committee to determine whether a run for the seat would be viable and resigned from his job at the Middlesex district attorney’s office.

Democrats’ reaction to his potential candidacy has been positive, many viewing him as next in line to carry on the Kennedys’ political success. According to poll statistics released Thursday by the University of Massachusetts Lowell and the Boston Herald, Kennedy would defeat Sean Bielat, a Republican, in the race for Frank’s seat by 2 to 1.

And for most at the caucus, where registered Democrats gathered to choose delegates for the state’s Democratic convention, Kennedy’s candidacy is a foregone conclusion.

Volunteers collected signatures, as required for him to appear on the ballot. People remarked “Go get ’em!’’ and “Good luck to you!’’ as he passed in the school’s hallways. Others took videos on cellphones. One woman declared, “I never do this!’’ when she asked Kennedy to pose with her for a photo.

Kennedy was modest about local Democrats’ confidence in his candidacy, demurring when asked about when he will announce his candidacy.

He maintained that his appearance at Newton’s Democratic caucus was not a bout of preliminary campaigning, but instead just an opportunity to see “what’s on people’s minds.’’

“People have been encouraging, and that’s been very humbling, but it’s a long way to go,’’ Kennedy said. “We’re going step by step.’’

Brooke Lipsitt, former president of the Newton Board of Aldermen, embraced Kennedy a few moments after he entered the caucus, shaking his hand and saying, “I remember meeting your dad when he was about to run for office!’’