Monday is the last day new voters can register in key swing state Virginia.
Long, who originally signed up as @not_THAT_Jlo but was able to switch to @justinlong, tweeted that he was convinced to join Twitter "after years of being a proud twitter-less Luddite" by Shiloh Jolie-Pitt. He went on to tweet from the bus tour, where he is accompanying Virginia Democratic Party Chairman Brian Moran, former Michigan Gov. Jennifer Granholm and Rep. Jim Moran (D-Va.).
Long and the Gotta Vote tour were in Iowa on Monday.
The actor also played Mitt Romney in a parody video for progressive advocacy group MoveOn.org earlier this year.