One Republican, John Fleming, has already jumped in to challenge Cassidy for the party’s Senate nomination next year. Fleming, who served four terms representing a western Louisiana district in the House, cited Cassidy’s impeachment vote in announcing his bid in December.

La., spoke on the Senate floor to explain his decision to support Robert F. Kennedy Jr.'s nomination to serve as health and human services secretary. Cassidy said it was a "long, intense process" for Kennedy but that he had committed to "collaboration" to address the wide range of health issues facing the nation.