Indiana steps into the national spotlight Tuesday with a primary election that could play a significant role in deciding Republican and Democratic presidential contests, as well as a spirited Senate GOP primary election and crowded races for Republican nominations in two U.S. House districts. Two state Senate Republican primaries also are drawing attention as Senate leaders try to fend off challenges.

Voters cast a record number of early ballots and high turnout is expected, especially in some heavily Republican counties in suburban Indianapolis.

PRESIDENTIAL STAKES

Candidates from both parties have traversed the state over the past two weeks, visiting local hotspots and flooding the airwaves with ads.

Indiana has 57 Republican and 92 Democratic delegates for their party national conventions this summer.

Thirty of the Republican delegates will go to the winner of the statewide primary vote. GOP rivals Donald Trump or Ted Cruz are likely to share the remaining 27 delegates as three are awarded to the winner in each of Indiana’s nine congressional districts. Trump is looking to strengthen his front-runner status. Ohio Gov. John Kasich effectively ended his Indiana campaign last week with a deal letting Cruz face Trump head on.

Indiana’s Democratic delegates are awarded based on the vote percentage for Hillary Clinton or Bernie Sanders in each congressional district.

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CONGRESS AND SENATE

Republican U.S. Reps. Marlin Stutzman and Todd Young are vying for the U.S. Senate seat now held by retiring GOP Sen. Dan Coats. They’ve had a contentious campaign during which Stutzman has characterized Young as an establishment pawn. Young has attacked the tea party-backed Stutzman as an ideologue who prioritizes obstructionism over passing legislation.

The winner will face former U.S. Rep. Baron Hill, who is unopposed for the Democratic nomination.

The Stutzman-Young Senate race prompted big fields of candidates for the congressional seats they are leaving.

In southern Indiana’s 9th District, the packed GOP contest includes state Attorney General Greg Zoeller as well as state Sens. Erin Houchin of Salem and Brent Waltz of Greenwood. First-time candidate Trey Hollingsworth has been accused of trying to buy the seat with more than $1.7 million from himself and his father after moving to Jeffersonville in September from his native Tennessee.

State Sen. Jim Banks of Columbia City faces agricultural businessman Kip Tom of Leesburg and fellow state Sen. Liz Brown of Fort Wayne for the 3rd District in northeastern Indiana.

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LEGISLATIVE LEADERSHIP CHALLENGES

Two top leaders of the Indiana Senate face Republican primary challengers attacking them over legislative moves in recent years after breezing through previous election cycles.

Senate President Pro Tem David Long of Fort Wayne faces criticism from social conservatives for pushing an unsuccessful proposal this year that would have extended state anti-discrimination protections to lesbian, gay and bisexual people. He faces John Kessler, director for Indiana University-Purdue University Fort Wayne’s Center for Economic Education.

Scott Willis, a Westfield business owner challenging Senate Appropriations Chairman Luke Kenley of Noblesville, argues Kenley hasn’t done enough to boost funding for schools and road projects in the fast-growing suburban area north of Indianapolis.

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HIGH TURNOUT

Early voting turnout has hit record highs with more than 270,000 people casting ballots ahead of the primary, according to the Indiana Election Division. Early voting totals through Sunday already were nearly 50 percent more than the state’s record for early voting set in the 2008 primary — which featured the tight race between Barack Obama and Clinton for the Democratic presidential nomination.

Election Division Co-Director Angie Nussmeyer said she doesn’t know whether the jump in early voting will mean higher turnout overall for the primary or shows more awareness of it as an option for voters. Higher turnout is anticipated in strongly Republican counties, such as Hamilton and Johnson counties in suburban Indianapolis.

About 62 percent of the applications for early or absentee voting have been for Republican ballots.

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VOTING ON TUESDAY

Polling locations around the state will be open 6 a.m. to 6 p.m. local time, so the 12 of Indiana’s 92 counties that are in the Central time zone close an hour after those in the Eastern time zone.

Voters can confirm their registration, find their polling sites and get information about candidates on their ballots online.