From U.S. News and World Report:

“The base is so strongly behind the president, despite his enormous weaknesses,” says Andy Smarick, director of civil society, education and work at the nonpartisan think tank R Street. “Is it worth challenging the base? I think they have decided it just doesn’t make sense to do so. This isn’t just speculation, that Republicans have to worry about their right flank,” adds Smarick, who worked in the George W. Bush White House. “It actually happens.”