Indiana Republican leaders met Wednesday to discuss how to handle allegations that a U.S. Senate campaign improperly tried to access a critical database of voter information.

Party chairman Eric Holcomb declined to comment on the matter, saying he wants to keep the discussion in-house. But the spat has added fuel to an already heated Republican primary between Sen. Richard Lugar and his tea party-backed challenger, Indiana Treasurer Richard Mourdock.

The Republican Party's voter files are incredibly important for any campaign, although especially so for Lugar and Mourdock as they enter the last few weeks before the election. Republicans use the data to determine who to target with phone calls, door knocks, direct mail and other tactics designed to bring their supporters to the polls.

At issue is a March 14 email obtained by The Associated Press in which Mourdock campaign manager Jim Holden writes that Mourdock staffers should "start pillaging email addresses" from a voter database known as Salesforce, which is used by all Indiana Republicans.

"We have a Salesforce login again. Can one of you guys login immediately and start pillaging email addresses like a Viking raider attacking a monestary full of unarmed monks?" Holden wrote. In the email, he also instructed them to take the information, "download into our house file" and remove duplicate entries.

A Republican official familiar with the problem told The Associated Press the Mourdock campaign's access to Salesforce was revoked shortly after the email was discovered. The official spoke on condition of anonymity because the investigation is ongoing.

The Lugar campaign quickly chastised Mourdock after learning about the investigation Wednesday.

"Mr. Mourdock must come clean and answer serious questions if he wishes to represent Hoosiers in the United States Senate," Lugar campaign manager Emily Krueger said in a statement.

But Mourdock spokesman Chris Conner denied that the campaign had accessed the software. He called the email a "joke" that was "taken out of context." He said he doesn't believe there was any wrongdoing.

Indiana Republicans rely on two voter databases. The first database, Voter Vault, is a national database maintained by the national Republican Party and mined for raw voter data by state parties. National Democrats use a similar system to bring voters to the polls who will vote for their candidates. Salesforce is the software used by the Indiana Republican Party and individually licensed to candidates for use.

If the Mourdock campaign did a mass download of the voter files as indicated in Holden's March 14 email, it may have violated its licensing agreement.

Mourdock presents a major challenge to the six-term incumbent Lugar in the May 8 Republican primary, relying largely on help from such national conservative groups as the Club for Growth and the National Rifle Association.