Vice President Mike Pence is recording a robocall for the Republican nominee in Tuesday's special House election in Kansas, a clear sign of concern that the Democrats could flip this solid GOP seat.

Sources told the Washington Examiner on Friday that Pence would record a call urging Republicans in Kansas' Wichita-area 4th district to get out and vote for state Treasurer Ron Estes, who is locked in a tight battle with Democrat James Thompson.

The White House political office, led by political director Bill Stepien, has joined what has become a party-wide effort to save a seat that President Trump won by nearly 30 points in November. The White House did not immediately respond to a request for comment.

"Ron's run a horrible campaign. Hasn't raised much money, his ads are abysmal — no energy," a Kansas Republican operative said, on condition of anonymity in order to speak candidly. "It's a low turnout special and weird things happen."

Most political insiders have been focused on an upcoming special House election in Georgia, where Democrat Jon Ossoff is polling well against a crowded field of Republicans running in the Atlanta-area 6th district. Except, that's a seat where Trump only defeated Hillary Clinton in November by 1 point.

As in the Georgia race, Democratic energy and enthusiasm are way up in Kansas' 4th district, and Republicans are worried enough that they have started pouring resources into the race in the last week.

Sen. Ted Cruz of Texas will be in the district Monday to campaign for Estes, BuzzFeed reported Friday. On Thursday, Politico reported that the National Republican Congressional Committee was going on television with an advertising buy.

"We're happy to help out in this small way and show our support for Ron Estes. We look forward to Ron coming to Congress and standing up for Kansas values," NRCC spokesman Matt Gorman said.

Kansas 4th district was previously held by Mike Pompeo, who was confirmed as Trump's CIA director in January.