Outgoing South Carolina Rep. Mark Sanford will pack up his House office in January, but not before sending a message. 

Sanford will not endorse his Republican primary rival Katie Arrington in her bid for his 1st District seat, he confirmed to the Post and Courier on Monday.

“Part of leadership, at times, means knowing when it’s best to keep quiet,” Sanford told the paper. “To me, this is probably one of those times.”

Sanford’s stance comes days before Election Day, as Arrington faces an unusually competitive contest in what is supposed to be a slam-dunk district for the GOP.

In her matchup against Democrat Joe Cunningham, Nathan L. Gonzales rates the district Solid Republican. Still, the National Republican Congressional Committee dropped $87,000 into the district this week, calling attention to the race. 

In a bruising primary battle, Arrington successfully challenged Sanford, a member of the deeply conservative Freedom Caucus, from the right. Support for President Donald Trump proved to be a decisive fault line. 

Arrington appealed to the Trump’s base, while Sanford was an occasional thorn in the president’s side on cable news. For example, he staked out opposition to Trump’s divisive and sometimes violent rhetoric in the wake of the shooting at the Republican team’s congressional baseball practice last year. He said the president’s verbal attacks were “partially” to blame for the country’s fierce political divisions.

Trump endorsed Arrington on Election Day. “Mark Sanford has been very unhelpful to me in my campaign to MAGA. He is MIA and nothing but trouble. He is better off in Argentina,” Trump tweeted.

Trump mocked Sanford’s subsequent defeat at a private meeting with Congressional Republicans. Sanford bristled that the president would pick on him given that on policy, they closely align.

To “shoot at a guy you’ve already shot and killed, is perplexing and unfortunate,” Sanford said to the Post and Courier at the time. “If you were to pick a group of folks who have been most aligned and most supportive of the president’s agenda, it would in fact be the Freedom Caucus.”

Sanford has occasionally diverged from the party line though, most notably on climate change.

“I believe human activity is having a measurable effect on the environment,” he wrote in a 2007 Washington Post op-ed.

Offshore drilling was a defining issue during the primary. Arrington distinguished herself from Sanford by offering full-throated support for the president’s plan to allow for offshore oil and natural gas drilling in federal waters off the Atlantic Coast, referring to the rule change as an “America First policy of true American energy independence.” Sanford was an outspoken opponent.

Arrington has since reversed her position. 

The 1st District stretches alongside state’s Lowcountry shoreline, which will face more flooding, shoreline erosion and loss of coastal wetlands as global temperatures rise, according to the Coastal Conservation League, a South Carolina environmental group.

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