Representative Dean Phillips, a Minnesota Democrat who has for months been saying in public what many in his party only whisper in private — that the 80-year-old President Biden should not seek re-election because of his age — said he was considering challenging Mr. Biden in next year’s primary.
Mr. Phillips, 54, is in his third term in Congress representing a district that includes the suburbs west of Minneapolis. In a text message, he confirmed his interest in running but declined a request to be interviewed. He said he had “been overwhelmed with outreach and encouragement” and needed to assess his next steps.
Mr. Phillips would be an extreme long shot if he were to challenge Mr. Biden. Polls show that Democrats, who were once wary about Mr. Biden seeking re-election, have coalesced behind him. The party’s major donor class is backing the president, who raised $72 million with the Democratic National Committee and his joint fund-raising committee during the three-month reporting period that ended June 30.
Mr. Phillips had $277,000 in his congressional fund-raising account at the end of June.
An heir to a Minnesota liquor fortune who showcased himself driving a gelato truck in his first House campaign, Mr. Phillips has been known in Congress for embracing the moderate suburban politics that were at the core of the general election coalition that propelled Mr. Biden’s 2020 victory. He was first elected in 2018, when he and dozens of fellow Democrats flipped Republican-held districts as suburban voters turned against President Donald J. Trump.
In Congress, Mr. Phillips has received attention for his outspoken calls for aging members of the Democratic Party to step aside. He said last year that Mr. Biden should not seek re-election, and he has called for the resignation of Senator Dianne Feinstein of California, whose health has visibly deteriorated in recent months.
The Biden campaign and the D.N.C. have so far declined to comment about Robert F. Kennedy Jr. and Marianne Williamson, who began their own primary campaigns against Mr. Biden this year. Officials from both the D.N.C. and the Biden campaign declined to speak about Mr. Phillips.