Republican U.S. Sen. David Perdue and Democrat Jon Ossoff will face off in a Jan. 5 runoff in Georgia for Perdue’s Senate seat. Libertarian candidate Shane Hazel was able to get enough votes to prevent either candidate from clearing the 50% threshold needed for an outright win.

The contest has already seen huge spending from outside groups on both sides and millions of dollars more are expected to pour into the state ahead of the runoff. Perdue is a close ally of President Donald Trump. The race has been characterized by sharp attack ads but relatively moderate political positions.

Coupled with another runoff in Georgia in a special election, the two Senate races could decide which parties have control of the US Senate.