(WENY) -- President Donald Trump will be holding a rally at the Williamsport Regional Airport on Monday in Pennsylvania, ahead of voters in the district taking to the polls on Tuesday. 

Trump is backing Republican contender Fred Keller, who is going up against Democrat Marc Friedenberg. The two candidates are fighting for Republican Tom Marino's vacant 12th congressional district seat. Marino resigned in January for a job in the private sector, just two weeks after being sworn in. 

Keller is a former business manager, and current State Representative. According to Keller's campaign website, the issues he's most focused on include supporting PA's farming families, and building infrastructure, especially in rural areas. 

Friedenberg works at Penn State University as a instructor in the College of Information, Sciences and Technology. Friedbenberg's priorities include jobs, health care, social security and access to broadband internet. 

The special election is happening on Tuesday, May 21st.

WENY News will be at the Trump rally on Monday and we'll bring you live coverage on air and keep you informed throughout the day online at weny.com, and on Facebook and Twitter.