Of the 100 seats in the upper chamber, 34 are in play Tuesday, and Democrats are looking to maintain their slim majority while the GOP is eyeing control. Hurting the Democrats’ chances are departures by independent Sen. Krysten Sinema of Arizona, formerly a Democrat, and Sen. Joe Manchin of West Virginia.

Democrats and Republicans are battling for control of the U.S. Senate this election. There are 34 Senate seats up for grabs, with about a half dozen of those likely to be decided by tight margins. The winners of each race will serve six-year terms in the Senate.