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"Like I said in the beginning it isn't a me, it is a we moment." Katie Arrington said as she defeated U.S. Rep. Mark Sanford on Tuesday, June 12, 2018 in North Charleston. Andrew Whitaker/Staff

Katie Arrington ran a simple but effective campaign against U.S. Rep. Mark Sanford, embracing the ethos of President Trump while repeatedly telling GOP primary voters the one thing that ultimately mattered: Mr. Sanford was not on board with Team Trump.

“We are the party of Donald J. Trump,” Ms. Arrington told a cheering crowd Tuesday night at her victory party in North Charleston.

Ms. Arrington’s win was the latest signal that the South Carolina Republican Party continues to lean Mr. Trump’s direction, and is willing to leave behind more moderate establishment figures like Mr. Sanford and anyone else who dares criticize the president. The fiscal conservative had never lost an election, managing to overcome high-profile personal issues over the years. But he used up the last of his nine lives against Ms. Arrington and her MAGA enthusiasm.

Ms. Arrington, a first-term state lawmaker, got a late boost with an endorsement from Mr. Trump about three hours before the polls closed. It was classic Trump — a biting, personal insult aimed at Mr. Sanford and launched via Twitter.

But it was the Trump loyalty test that proved to be Ms. Arrington’s most powerful Sanford kryptonite. There must have been some talk about issues over the past few months, but her campaign — helped by a Trump campaign adviser — decided to make the contest a referendum on fealty to the president. It was effective in a state where Mr. Trump won 55 percent of the vote in 2016 and remains popular today.

Elsewhere around the country, allegiance to Mr. Trump helped push a Virginia county supervisor to a GOP Senate primary win. And an Alabama congresswoman now faces a runoff, the penalty for angering voters who remember her calling on Mr. Trump to end his 2016 presidential bid after the release of a video of him joking about grabbing women.

Candidates often pander to their bases in primaries, which makes sense from a purely political view. Party loyalists are the ones heading into the voting booth in these typically low-turnout elections. But it would be helpful to voters — in South Carolina and the rest of the country — if campaigns relied more on ideas and solutions than allegiances and loyalty tests. Hopefully we’ll see more of that during the general election campaign.

The victory for pro-Trump forces was not complete Tuesday in South Carolina. Gov. Henry McMaster, an early Trump backer and also the proud recipient of a presidential endorsement, garnered the most votes in his GOP race but could not pull clear of businessman John Warren.

There still may be limits to how much influence the Trump imprimatur has on an election, but winning outright in a five-way primary would have been impressive. It remains to be seen if Mr. Trump will campaign for Mr. McMaster ahead of the runoff election.

GOP primary voters in South Carolina indicated Tuesday that they want more candidates who adhere to the Trump doctrine. Sometimes that will mean pushing out once popular politicians to make room for those willing to embrace the Trump experience. So while the president won’t be on the ballot this year, expect to hear more about him in the coming months.