(CNN) - An Indiana group called Hoosiers for a Conservative Senate will hold a straw poll later this month to endorse a GOP candidate to primary challenge longtime Republican Sen. Richard Lugar.
The group tells CNN that their convention will be held on September 24th in Greenfield, Indiana and that it will include both a convention style format and a straw poll, with two delegates each from 55 tea party groups from across the state voting. Hoosiers for a Conservative Senate will make their Senate endorsement based on the results of the straw poll vote.
Thursday Lugar's re-election team told CNN that the senator will decline an invitation to attend the event.
Hoosiers for a Conservative Senate was formed last October to try and find a conservative candidate to take on Lugar in next year's primary. Some national fiscal conservative groups, like FreedomWorks and Club for Growth, are also trying to unseat Lugar, as he battles for a seventh term in the Senate.
Lugar is facing a primary challenge from the right, from Indiana State Treasurer Richard Mourdock, who announced his bid on February 22. Lugar has a huge advantage of Mourdock when it comes to campaign cash.
Greg Fettig, one of the founders of Hoosiers for a Conservative Senate, says that Mourdock has accepted an invitation to attend the convention.
"Never before has the tea party anywhere in the nation worked in such a coordinated and cooperative effort on a singular task in the name of restoring constitutional conservatism and a heartland common sense in Washington" says Fettig.
Lugar is the most senior Republican member of the Senate. He's been criticized by many tea party activists and other grass-roots conservatives for his willingness to work with Senate Democrats to seek bipartisan solutions, for his votes in favor of President Obama's Supreme Court nominees the past two years, and for his 2008 vote in favor of the Troubled Asset Relief Program, better known as TARP. They were also upset with him for his early public openness last year to vote in favor of the New Strategic Arms Reduction Treaty (New START) with Russia.
The 79 year old lawmaker was first elected to the Senate in 1976 after serving as mayor of Indianapolis. Lugar did not face a primary challenge in 2006 and won 87 percent of the vote in the general election, facing only a libertarian candidate.
The GOP primary is set for May 8, 2012.
Rep. Joe Donnelly is currently the only announced Democratic candidate in the race.
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