Detailed accounts of the final hours of the negotiations show that, while the United States offered Canada what it said was the best deal of any country, what Canada had to give up in exchange was seen as unthinkable.
The administration asked the court to clear the way for President Trump's order that creates "state citizenship lists" and directs the Postal Service to decide who gets a mail-in ballot.
Republicans still have some clear advantages on the map, but President Trump's unpopularity has opened the door for an outcome that once seemed far-fetched.
The 68-year-old tourist and his companion were driving through Death Valley National Park on a remote road last week when their car got stuck in mud, officials said.