As President Trump criss-crosses the country on Air Force One during the final days of the midterm campaign, a trio of Democratic senators are demanding information about whether the White House is properly reimbursing taxpayers for campaign-related travel.  

Sens. Ron Wyden (D-Ore.), Jeff Merkley (D-Ore.) and Ed Markey (D-Mass.) argue there have been multiple instances throughout Trump’s presidency when he traveled out of town for an official event but engaged directly in political activity, such as calling for the election of a certain candidate. It amounts to a “frequent blurring of the lines” between official and campaign events, the senators say, and they’re asking the White House to hand over documents that may shed light on how it has compensated taxpayers for political expenses. 

“It is essential that taxpayer dollars are not used to subsidize partisan political activities and that the White House comply with all laws and regulations that govern payment of expenses associated with president’s travel,” the senators wrote in the letter to interim White House counsel Emmet T. Flood. The letter was provided to The Washington Post in advance of its release. 

One example the senators said raised questions was a July 26 trade-related event at a steel plant in Granite City, Ill., that had not been billed explicitly as a campaign stop. But there, Trump told the crowd: “You’ve got to vote Republican, folks, you’ve got to vote Republican. . . . Vote for these two congressmen; they know what we’re doing. They know what they’re doing.” 

At the time, a White House spokesman said “there is no legal prohibition” on endorsing political candidates at official, taxpayer-funded events. And Wyden, Merkley and Markey noted in their letter to Flood that Federal Election Commission records show Trump’s campaign committee has paid for some political travel.

 Still, the senators said they have questions regarding “how the White House has apportioned expenses, and to what extent any payments have been sought retroactively on behalf of taxpayers.” They are asking Flood to respond to their request for documents by Nov. 7.