A tape recording of Donald Trump making disparaging remarks about women has sparked howls of condemnation from Republican colleagues. Several have said they can no longer back him.
It's not the first time. 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
■Susan Collins, Maine senator
■Dan Sullivan, Alaska senator
■Lisa Murkowski, Alaska senator
■Kelly Ayotte, New Hampshire senator
■Jeff Flake, Arizona senator
■Dean Heller, Nevada senator
■Mark Kirk, Illinois senator
■Ben Sasse, Nebraska senator
■Mike Crapo, Idaho senator
■Cory Gardner, Colorado senator
■Lindsey Graham, S Carolina senator
■John Thune, S Dakota senator
■Deb Fischer, Nebraska senator
■John McCain, Arizona senator
Other Republicans who have deserted him
■Jeb Bush, former Florida governor
■Tim Pawlenty, former Minnesota governor
■Gary Herbert, Utah governor
■Jason Chaffetz, Utah congressman
■Carly Fiorina, former presidential candidate
■Barbara Comstock, Virginia congresswoman
■Mike Coffman, Colorado congressman
■Mike Lee, Utah congressman
■William Cohen, former secretary of defence
■Michael Hayden, former CIA director, former NSA director
■John Kasich, Ohio governor, 2016 presidential candidate
■Tom Ridge, former Pennsylvania governor; former Homeland Security secretary
■Mitt Romney, former Massachusetts governor, 2012 nominee
■Ileana Ros-Lehtinen, Florida congresswoman
Republicans voting for Mrs Clinton
■Ex-President George HW Bush
■Richard Armitage, former deputy secretary of state
■Hank Paulson, former treasury secretary
■Brent Scowcroft, former national security adviser
■Richard Hanna, New York congressman
■Chris Shays, former Connecticut congressman
■Meg Whitman, prominent Republican donor; CEO of Hewlett Packard
Senior Republicans still in Trump's corner
■Ted Cruz, Texas senator
■Ben Carson, retired neurosurgeon, 2016 Republican presidential candidate
■Chris Christie, New Jersey governor
■Newt Gingrich, former House speaker
■Rudy Giuliani, former New York mayor
■Mitch McConnell, Senate majority leader
■Paul Ryan, House speaker
■Marco Rubio, Florida senator, 2016 Republican presidential candidate
■Scott Walker, Wisconsin governor, 2016 Republican presidential candidate
Here’s a list of which Republicans are breaking away from Donald Trump