The rivals for the Republican nomination for U.S. Senate each filed his declaration of candidacy Tuesday with the Indiana secretary of state's office.

The campaigns for Sen. Richard Lugar, R-Ind., and Richard Mourdock said they submitted paperwork required to be placed on the May 8 ballot in the GOP primary election.

The filing deadline is noon Friday. A Senate candidate must collect the verified signatures of at least 500 registered voters in each of Indiana's nine congressional districts to earn a spot on the ballot.

"Having over 13,000 registered Hoosier voters indicating they are ready for Sen. Dick Lugar to defend his 36-year voting record in the U.S. Senate speaks volumes about the political mood in Indiana," Mourdock, the second-term state treasurer, said in a statement about the number of signatures he gathered.

He said voters "want new leadership in the U.S. Senate committed to true conservative values."

Lugar's campaign announced last month that it had collected nearly 6,400 voter signatures that it was delivering to county election officials for verification.

"Signatures on Senator Lugar’s petitions far exceeded the number required by Indiana law and showed early statewide support and continued momentum,” Emily Krueger, Lugar's campaign manager, said in a statement.

Krueger also said, "Clearly, these voters recognize the importance of having Dick Lugar fighting for Indiana jobs, cuts in federal spending and comprehensive tax and regulatory reforms.”