Congress rarely takes serious disciplinary steps against its own members, unless their ethical misdeeds rise to a federal crime. The last House member expelled was James A. Traficant Jr., Democrat of Ohio, in 2002, after he was convicted of 10 felony counts including bribery, racketeering and tax evasion.
The House Ethics Committee, a bipartisan panel of lawmakers who have historically shied away from punishing their colleagues, has not commented on Mr. Santos’s case and is in a state of limbo until a new Congress is seated on Jan. 3. Were the panel to launch an inquiry once Mr. Santos becomes a member of Congress, its investigations are known to drag on for months or even years and seldom result in a significant punishment.
Members are at times issued fines or made to stand in the well of the House for a public censure.
That occurred in the case of former Representative Charles B. Rangel, the powerful New York Democrat. The House voted in 2010 to censure Mr. Rangel, the most severe sanction it can administer short of expulsion, after an Ethics Committee investigation found that he had broken congressional rules by failing to report taxes on rental income from a villa in the Dominican Republic and misused his office to solicit fund-raising donations.
It’s unclear whether lying to voters before taking office — by itself — would be a violation within the jurisdiction of the Ethics Committee, but campaign finance improprieties and making false statements on disclosures are often grounds for investigation. House rules also prohibit acting in a matter that brings discredit to the House.
Some embattled members have chosen to resign, especially under pressure from party leadership. Representative Katie Hill, Democrat of California, resigned in 2019 as she faced a House ethics investigation into allegations that she had a sexual relationship with a member of her congressional staff, a violation of House rules.
Democrats were quick to call on Mr. Santos to step down.
Representative Hakeem Jeffries, Democrat of New York and the incoming House minority leader, blasted Mr. Santos last week.
“He appears to be a complete and utter fraud. His whole life story made up, and he’s going to have to answer that question: Did you perpetrate a fraud on the voters?” Mr. Jeffries told reporters in Washington.
