The nastiest and most expensive Senate primary race in the nation reaches its conclusion tonight as three Republican candidates face off to challenge Sen. Joe Donnelly, D-Ind.

Businessman and former state Rep. Mike Braun, Rep. Luke Messer, and Rep. Todd Rokita have spent millions of dollars targeting each other with negative advertising, each vying to be the most pro-Trump Republican candidate in the Indiana race.

Indiana uses an open primary system, meaning that voters are not required to register with a party to vote in a party primary. The polls close at 6 p.m. CT and ET, depending on which part of the state voters live in.

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