05/08/2012 02:58 pm ET Updated May 08, 2012

Dick Lugar, Richard Mourdock Senate Battle In Indiana Could Affect House Races

While the battle for the Republican Senate nomination has taken center stage in Tuesday's Indiana primary, the fight could affect turnout in three open congressional races further down the ticket, two of which feature Tea Party-backed candidates.

Polls show a tight race between Sen. Richard Lugar and State Treasurer Richard Mourdock, a Tea Party favorite who has invigorated the district's conservative base. That energy, dubbed the "Mourdock effect," could well jumpstart the biggest upset Tea Party upset yet, and -- if the voters energized by Mourdock vote their values down the ticket -- not just at the Senate level, but at the House level as well.

"I just think Lugar has become less conservative over the years and I think it's time for someone new," 27-year-old Chris Creech told the Associated Press after voting at the Good Shepherd United Methodist Church in Indianapolis.

In the 8th district, Mourdock's hometurf, Tea Party favorite Kristi Risk has mounted a significant challenge to freshman Rep. Larry Bucshon. While Buschon is expected to beat out his primary competition, Risk came in fewer than 2,000 votes behind him in the 2010 Republican primary, and the Tea Party activists energized by Mourdock's campaign are the same ones likely to support her.

The 5th district, where GOP Rep. Dan Burton's exit will open up the field for a less polarizing conservatives, is more of a wildcard. Repeat candidate John McGoff is a Tea Party favorite while ex-Rep. David McIntosh has the backing of national conservative groups such as the Club for Growth, and both appeal to the sorts of strong conservatives backing Mourdock. Former U.S. Attorney Susan Brooks and Marion Mayor Wayne Seybold are also in the running.

The race to replace Republican Rep. Mike Pence in the 6th district has also attracted some attention, with former state party official Luke Messer, who enjoys all the advantages of name recognition, facing off an impressive challenge from Republican Travis Hankins.

Early voting is down 40 percent from 2008, Clerk's office spokeswoman Angie Nussmeyer told The Associated Press, with officials predicting a statewide turnout of 17 to 20 percent, roughly 10 percentage points down from the high-turnout election of 2008.