(CNN) - With less than four days before the Indiana Senate primary, incumbent Sen. Dick Lugar and his challenger Richard Mourdock made their closing arguments in new television ads released Friday - the final spots of a long, often-times ugly nomination battle.
"America faces serious challenges, but Hoosiers' courage and determination are unbreakable. It's this spirit that guides me every day in the Senate," Lugar says in the ad, "Spirit."
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The most senior Republican in the Senate, Lugar is fighting to keep his seat and move on to a seventh term in office. Mourdock, the state's treasurer with a large tea party backing, represents the most serious primary threat for Lugar since the senator was first elected 35 years ago.
In the ad, which makes no mention of Mourdock, Lugar touts his legislative record, highlighting his opposition to President Barack Obama's sweeping healthcare reform.
"My job has been and always will be to live up to the ideals of our state," Lugar says in the commercial, as footage shows the senator meeting with various supporters during the campaign.
Mourdock, on the other hand, did mention his opponent in his new ad, saying the incumbent senator "has spent thousands of dollars telling you things about me that he knows are not true."
"He thinks this campaign's about me, but it's not. It's not about him either. It's about America's future," he added.
Mourdock went on to say the election was about "spending less, padding down our debt and restoring opportunity and freedom."
His words mirror a main theme from Mourdock's campaign and that of other groups critical of Luar, arguing the longtime senator is a Washington senator with a key role in increased spending on Capitol Hill over the years.
"I'm Richard Mourdock and I approve this message because the truth is, it's time for new conservative leadership in Washington," Mourdock says, concluding the ad.
The commercials cap months of ads lunched by the two campaigns. Many of the spots were largely negative, symptoms of what's been one of the most heated Senate fights this primary season.
National figures have also weighed on the race. Mourdock has the backing of former Alaska Gov. Sarah Palin and former presidential candidate Michele Bachmann, while Sen. John McCain and popular Indiana Gov. Mitch Daniels are siding with Lugar.
Recent polls show the race in a dead heat, even within days before voters head to the polls on Tuesday.