Who is the driving force behind the nomination of Leffingwell in the novel, Advise and Consent?

The President of the United States, never named, is the driving force behind the nomination of Leffingwell. The President is in his seventh year in office. He is a member of the Majority party and popular with the people of the country. He brings every ounce of weight he can to bear on getting Leffingwell confirmed. To this end he becomes a political animal, doing whatever is necessary to secure the votes –from alerting Ackerman to Anderson’s past to attempting to bribe Knox with endorsement for the Presidency in the next election.