President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE has endorsed Pennsylvania Republican state Sen. Rick Saccone in his bid to win a Pittsburgh-area House special election in March, an endorsement that came hours before Trump traveled to the district.

Trump tweeted his support for Saccone Thursday morning, arguing that he will help to move his agenda forward in Washington.

Will be going to Pennsylvania today in order to give my total support to RICK SACCONE, running for Congress in a Special Election (March 13). Rick is a great guy. We need more Republicans to continue our already successful agenda! — Donald J. Trump (@realDonaldTrump) January 18, 2018

But the tweet could put the White House and the Republican National Committee (RNC) in a tricky spot ahead of the visit as the source of funding for the trip becomes an issue.

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The taxpayers fund presidential travel for official trips but political parties are required to reimburse the White House for a portion of a trip that involves political activity.

The White House had framed Trump's trip, which includes a speech at a manufacturing company touting the GOP's successful tax-reform push, as official business and not a campaign stop. While Saccone is expected to attend, the White House had told The Associated Press that Trump wasn't going to mention the GOP candidate explicitly.

With that speech set in the very district that is holding a special election in less than eight weeks, the subtext was clear.

Now, Trump's tweet removes any of that subtext and could raise questions as to who is paying for the trip.

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A 2012 report by the Congressional Research service explains that "when travel involves both official and political functions, the White House uses a formula to determine" the reimbursement from the political committee.

White House press secretary Sarah Huckabee Sanders denied the idea that the trip had political motivations in a statement to reporters, even as Trump called the visit "in order to give my total support to Rick Saccone."

"The President is enthusiastic about today's trip to Pittsburgh, Pennsylvania to discuss the incredible successes his tax plan is already achieving for the American people," she said.

"While the President has made clear his support for Republican candidates throughout the country, including in Pennsylvania, the purpose of today's visit is to promote the President's successful agenda especially on taxes."

The White House has not responded to questions as to whether it would seek reimbursement for any part of the trip, but the statement suggests it will not.

The Hill has reached out to the RNC to clarify whether the political portion of the trip will be reimbursed.

While running for president in 2016, Trump blasted then-President Obama for putting the taxpayers on the hook when he traveled to support Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE's presidential bid.

Taxpayers are paying a fortune for the use of Air Force One on the campaign trail by President Obama and Crooked Hillary. A total disgrace! — Donald J. Trump (@realDonaldTrump) July 5, 2016

Updated: 11:44 AM EST.