In the 1970 elections, he gave up his House seat to run on the Democratic ticket for United States Senator from New York. In the 1970 election, Ottinger split the liberal vote with the Republican (and Liberal-endorsed) nominee, incumbent Senator Charles Goodell (who was appointed by Governor Nelson Rockefeller after the assassination of Senator Robert F. Kennedy). Both were defeated by the nominee of the Conservative party, James L. Buckley in a three-way race.