Alex Mooney defeats David McKinley, a House colleague, in a newly drawn district.

Representative Alex Mooney handily defeated a House colleague and fellow Republican, David McKinley, in a primary in West Virginia that again proved both the power of an endorsement by former President Donald J. Trump and the weight that right-wing ideology holds with Republican primary voters.

Mr. Mooney, a four-term House Republican known more as a conservative warrior than a legislator, used Mr. Trump’s endorsement to overcome a distinct disadvantage: The redrawn district he was running in included far more of Mr. McKinley’s old district than Mr. Mooney’s.

The huge margins Mr. Mooney was able to run up in the fast-growing counties from his old district along the Maryland state line proved too great for Mr. McKinley, and the result was called on Tuesday night by The Associated Press. But Mr. Mooney’s victory stretched deep into Mr. McKinley’s home turf, blanketing the new district, including counties in the West Virginia panhandle that jut between Ohio and Pennsylvania.

It was a thorough repudiation of Mr. McKinley’s pragmatism, which led him to vote for the $1.2 trillion bipartisan infrastructure bill co-written by West Virginia’s centrist Democratic senator, Joe Manchin III, and for the creation of a bipartisan commission to examine the Jan. 6 attack on the Capitol.

“He is a liberal RINO Republican,” Mr. Mooney said of his opponent at his closing rally last week, using the acronym for “Republicans in name only,” a conservative slur. “In order for our party to be successful, we need to take these RINOs out in primaries.” Mr. Mooney promised he “would fight for the values of our country, not go along to get along with the Democrats.”

Mr. Mooney’s convincing win is all the more stunning in a state that once revered politicians, such as Senator Robert C. Byrd, who brought back copious amounts of money from Washington to help the impoverished hills and hollers of Appalachia.

Mr. Mooney had blanketed the state with radio and television advertisements that featured Mr. Trump offering him the former president’s “complete and total endorsement,” while slamming Mr. McKinley for voting for the infrastructure bill and the Jan. 6 commission.

But Mr. Trump did not sweep into the state for a last-minute get-out-the-vote rally, a decision that campaign aides to Mr. McKinley had hoped would keep the race close. Mr. McKinley had the backing of West Virginia’s governor, Jim Justice, and Mr. Manchin. And he had hoped the infrastructure bill would be an asset, not a liability.

But that appeared to be a miscalculation, as West Virginia is also a place that gave Mr. Trump 69 percent of the vote in 2020.

By turning the primary into a contest between a Trump-focused partisan and an incumbent running on his record of legislating, the two Republicans elevated the race for the Second District into something of a signal of how a possible Republican House majority might govern next year. In the end, ideology won out easily. Mr. Mooney had voted against certifying the 2020 election for President Biden, while Mr. McKinley agreed Mr. Biden had won.

If Republicans do control the House, the results might bode poorly for the business of governance, such as keeping the government funded and paying its debts once the federal government bumps into its borrowing limit.

The Club for Growth, a conservative political action committee that split with Mr. Trump in the Republican Senate primary in Ohio but also backed Mr. Mooney in West Virginia, was exultant.

“The result of this bellwether race is a clear sign that Republicans want their members of Congress to be real conservatives as opposed to moderate RINOs,” the group’s president, David McIntosh, said.