President Donald Trump endorsed Pennsylvania Republican state Sen. Rick Saccone in a March special election for a U.S. House seat. The endorsement was made in a tweet that came hours before Trump traveled to the Pittsburgh-area district Saccone hopes to represent.

Trump tweeted his “total support” for Saccone Thursday morning, insisting that the candidate will help Republicans continue their “already successful agenda.”

“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!”

Trump’s tweet brings into question the source of the funding of his trip, since taxpayers fund official presidential travel, but political parties — such as the Republican National Committee, in this case — are required to reimburse the White House for a portion of a trip that involves political campaigning.

The president’s trip, which includes a speech at a manufacturing company that will laud the Republicans’ tax reform plan, was framed by the White House as an official business trip. Saccone is expected to be present at the event, but the White House said that Trump had no plans to mention the candidate in his remarks.

According to a 2012 report by the Congressional Research Service, “when travel involves both official and political functions, the White House uses a formula to determine” that reimbursement.

During the 2016 presidential campaign, Trump criticized then-President Barack Obama for relying on taxpayers to fund his travel when he appeared in support of Democratic nominee Hillary Clinton.