– President Donald Trump's re-election campaign has demanded that a Minnesota Republican running for Congress stop using an old presidential tweet to promote his new campaign in a crowded GOP primary race.

"Your 2020 campaign's use of President Trump's 2018 endorsement, in any form, unfairly confuses voters," an attorney for the Trump campaign wrote in a Nov. 25 letter to Dave Hughes, a candidate for the Republican nomination in Minnesota's Seventh Congressional District.

Hughes, a retired Air Force major from Karlstad, won Trump's backing last year to challenge U.S. Rep. Collin Peterson, a 15-term Democrat who beat him by 4 percentage points. Trump weighed in on his Twitter account in September of 2018, writing: "Dave has my total endorsement."

But this year, Hughes is one of five Republicans running in the western Minnesota district that Trump carried by a big margin in 2016. The president's tweet is featured prominently on Hughes' campaign fliers, website, Twitter profile page and other promotional materials.

Hughes said through a spokesman that he "was honored to receive President Trump's endorsement in September 2018, and has been 100 percent honest with the voters and delegates in western Minnesota that this was a past endorsement."

The spokesman, Johnny Moyer, said the campaign would "continue to work with" the Trump campaign's lawyers on the matter.

By Tuesday afternoon, after a Star Tribune story went online, the Trump tweet had been removed from the front page of Hughes' campaign website. But it was still pinned at the top of Hughes' Twitter profile.

Among Hughes' rivals for the Republican Party endorsement is former Lt. Gov. Michelle Fischbach. Peterson, a conservative Democrat who has held on in an increasingly Republican district, has not yet said if he'll run for re-election next year.

Though Trump has not endorsed Fischbach, she alone among the GOP's Seventh District candidates was invited to speak on behalf of the president at an anti-impeachment rally in Detroit Lakes, Minn., in October organized by the Republican National Committee.

Fischbach has rounded up other establishment support, including endorsements by House Minority Leader Kevin McCarthy and former U.S. Rep. Michele Bachmann. As of Sept. 30, she had raised more than $100,000 for the race, compared to just under $37,000 raised by Hughes.

"I'm working hard to gain the support of delegates for the Republican endorsement," Fischbach said in a statement. "I'm confident we can succeed and also gain the support of President Trump."

Hughes suggested in a statement to the Star Tribune that political forces in Washington are meddling in the race. "Some career politician is using D.C. swamp tactics to try to deter my campaign from sharing with the voters that I was endorsed by the president," he said. He did not specify who he's referring to.

Neither the Trump campaign nor E. Stewart Crosland, the attorney who wrote the letter on the president's behalf, immediately responded to requests for comment.

But the campaign's letter made it clear that the Hughes endorsement had reached its expiration date.

"The Trump campaign reiterates its demand that your campaign cease and desist from all activities suggesting President Trump supports your primary candidacy," read the letter from Crosland, who works for Jones Day, a politically influential D.C. law firm.

Crosland first wrote to Hughes on Nov. 5, according to a copy of his letter provided by the Hughes campaign.

In that letter, he wrote that failure to comply would lead the Trump campaign "to consider all options available to it to make the record clear — whether in law or the court of public opinion."

In a letter back to Crosland the same day, Hughes wrote that he had always identified the endorsement tweet as being from 2018 and said he would continue to do so. Hughes also wrote that, "to avoid any confusion," he had halted the production of campaign T-shirts bearing Trump's '18 tweet.

But Crosland's Nov. 25 letter said that was not good enough:

"Unless and until the president and his campaign formally endorse your 2020 run, the Trump campaign demands that you remove all reproductions of the president's September 8, 2018, tweet from your 2020 campaign's website, social media, advertisements and merchandise."