Democrat Kamala Harris faced Republican Donald Trump on Tuesday in the U.S. presidential election, after the two candidates vied for support by staking positions on issues including abortion, the economy and foreign policy.

The most common disruptions at precincts are late openings, lack of staffing and voting machine issues, according to Jeff Greenburg, a 13-year election director veteran. He is now a senior advisor on election administration for The Committee of Seventy, a nonpartisan organization focusing on engagement and public policy advocacy.