Citigroup and Goldman Sachs, the marquee Wall Street firms on Mr. Santos’s campaign biography, told The Times they had no record of his ever working there. Officials at Baruch College, which Mr. Santos has said he graduated from in 2010, could find no record of anyone matching his name and date of birth graduating that year.

There was also little evidence that his animal rescue group, Friends of Pets United, was, as Mr. Santos claimed, a tax-exempt organization: The Internal Revenue Service could locate no record of a registered charity with that name.