Here’s a list of some of the leading Republicans who have deserted him since the tapes were revealed.
But it’s not the first time Mr Trump has lost support from colleagues. Republicans have been deserting him for months over various scandals.
So who is on the “Never Trump” list and who’s still on Mr Trump’s side?
Republican senators not voting for Mr Trump
- Kelly Ayotte, New Hampshire
- Susan Collins, Maine
- Mike Crapo, Idaho
- Deb Fischer, Nebraska
- Jeff Flake, Arizona
- Cory Gardner, Colorado
- Lindsey Graham, S Carolina
- Dean Heller, Nevada
- Mark Kirk, Illinois
- John McCain, Arizona
- Lisa Murkowski, Alaska
- Rob Portman, Ohio
- Martha Roby, Alabama
- Ben Sasse, Nebraska
- Dan Sullivan, Alaska
- John Thune, S Dakota
Republican Congressmen and Congresswomen not voting for Mr Trump
- Jaime Herrera Beutler, Washington
- Bradley Byrne, Alabama
- Jason Chaffetz, Utah
- Barbara Comstock, Virginia
- Mike Coffman, Colorado
- Rodney Davis, Illinois
- Jeff Fortenberry, Nebraska
- Scott Garrett, New Jersey
- Kay Granger, Texas
- Steve Knight, California
- Cresent Hardy, Nevada
- Joe Heck, Nevada
- Will Hurd, Texas
- John Katko, New York
- Mike Lee, Utah
- Frank LoBiondo, New Jersey
- Mia Love, Utah
- Patrick Meehan, Pennsylvania
- Erik Paulsen, Minnesota
- Tom Rooney, Florida
- Ileana Ros-Lehtinen, Florida
- Mike Simpson, Idaho
- Chris Stewart, Utah
- Fred Upton, Michigan
- Ann Wagner, Missouri
Other Republicans who will not vote for him
- Robert Bentley, Alabama governor
- Jeb Bush, former Florida governor and candidate for the 2016 nomination
- William Cohen, former secretary of defence
- Dennis Daugaard, South Dakota governor
- Carly Fiorina, former candidate for the 2016 nomination
- Darryl Glenn, from Colorado, running for the Senate
- Kim Guadagno, lieutenant governor of New Jersey
- Michael Hayden, former CIA director, former NSA director
- Gary Herbert, Utah governor
- Bill Haslam, Tennessee governor
- Jon Huntsman, former Utah governor
- John Kasich, Ohio governor, 2016 presidential candidate
- Susana Martinez, New Mexico governor
- George E Pataki, former New York governor
- Tim Pawlenty, former Minnesota governor
- Condoleezza Rice, former secretary of state
- Tom Ridge, former Pennsylvania governor; former Homeland Security secretary
- Mitt Romney, former Massachusetts governor, 2012 presidential nominee
- Brian Sandoval, Nevada governor
- Arnold Schwarzenegger, former California governor