The ethics charges rattled New York’s Democratic establishment, which considers Mr. Rangel political royalty, and touched off speculation about his future. The committee’s action comes days after the deadline for candidates to enter the Sept. 14 primary. Mr. Rangel faces four poorly financed opponents: Vince Morgan, a banker; Adam Clayton Powell IV, a state assemblyman; Jonathan Tasini, an activist, and Joyce Johnson, a former Obama campaign official.

There were indications on Thursday that New York’s Democratic leaders would rally around Mr. Rangel, at least for now. But at least one of his opponents, Mr. Tasini, called for the representative to drop out of the race, saying that his presence in the contest posed a “threat to the future of the Democratic Party.”

“The Republicans will make him the face of Washington corruption,” Mr. Tasini said. “It is not good for the party or for New York.”

The findings on Thursday were made by a four-member bipartisan investigative subcommittee of the full House Committee on Standards of Official Conduct. They will be aired at a public trial before an adjudicatory subcommittee, which will report to the full committee about whether it substantiated the findings. If the accusations are substantiated, the full committee then decides on what punishment should occur, from a letter rebuking him to a recommendation that he be expelled from the House.

The investigative panel began its work in September 2008 after The New York Times reported that Mr. Rangel accepted four rent-stabilized apartments from a developer at a price below market value, despite rules forbidding House members from taking gifts worth more than $50.

The units, one of which he used for his campaign, are in Lenox Terrace, a luxury complex in Harlem. Mr. Rangel paid a total of $3,894 monthly for the four units, while the market-rate rent for similar apartments in his building would total $7,465 to $8,125 a month, according to the Web site of the owner, the Olnick Organization.

After years of Mr. Rangel’s facing little opposition or scrutiny, the revelations about his arrangement set off a flurry of questions and aggressive examination of his personal finances and fund-raising.