For all its twists, turns and unprecedented developments of the 2016 campaign, one political reality remains in place: The demographic makeup of the Republican Party hasn’t changed much over the past 15 years. What has changed is the mood of the GOP electorate.

The Republican Party has been dominated by white, older conservative voters, as it was a generation ago. But, with much of the country becoming more diverse, younger and more liberal, many GOP voters are seething with frustration and anger.

Many Republicans feel “a sense of alienation from America, a sense that ‘this isn’t my country anymore,’ ” said Pete Wehner a former adviser to President George W. Bush. “Rather than find principled ways to accommodate themselves to the changes we’re undergoing, some Republicans are raging against them.”

That helps explain the emergence of Donald Trump, the businessman who has appealed to independents and other voters new to the Republican Party who are furious about immigration, economic stagnation and the failures of Republicans in Washington.

He appears to have succeeded in energizing the growing ranks of working-class voters—the ones former Minnesota Gov. Tim Pawlenty once called “Sam’s Club Republicans”—who have drifted into the party over the years but have had trouble, in the past, finding a presidential candidate or GOP message that could stir them to action.