DES MOINES, Iowa — Why now?

Despite his seemingly endless string of racist comments and insults about immigrants, Iowa Rep. Steve King had the Republican Party’s backing through nine elections and GOP presidential contenders often lined up for his endorsement in the state’s lead-off caucuses.

Now many of those same Republicans are turning their backs on King, stripping him of his committee assignments on Capitol Hill and even calling for him to leave office. A prospective 2020 GOP challenger already has emerged in his district.

The shift comes at a moment when the party is grappling with its stance on racial issues, in part because of President Donald Trump’s own inflammatory racial rhetoric and hardline views on immigration. GOP leaders also have conceded that the party must do better with minority voters and bring more diversity to their own ranks, currently dominated by white men.

There are also signs that King’s track record is wearing on voters in his overwhelmingly Republican district, which he carried by just 3 points in November.

“He barely won in a very, very conservative district and that signaled people are growing fatigued, getting tired of having to put up with some of the unnecessary heartburn,” said Bob Vander Plaats, a Republican who ran for Iowa governor in 2006 and leads the conservative group The Family Leader. “They don’t want to put up with it anymore.”

King’s insensitive remarks have included arguing “we can’t restore our civilization with somebody else’s babies” and predicting chaos if whites are replaced as the nation’s majority.

Yet Republican leaders still expressed shock following a recent New York Times story in which King expressed puzzlement about why terms like “white nationalist” are offensive, Republican leaders have expressed shock at his words, stripped him of his committee assignments and even questioned whether he belonged in Congress. The House voted 424-1 on Tuesday for a resolution repudiating King’s words.

Don Kass, a former Republican chairman in largely rural Plymouth County, argued that while comments by conservatives often are subjected to the worst-possible interpretation, King never should have discussed such terms as white supremacy. He said party officials might be turning against King because of his narrow win last November, coupled with that fact that his national notoriety translates into fundraising success for his Democratic opponents.

“He had a 3 percent victory that should have been 30 percent, and that’s not going to go away,” said Kass, a county supervisor.