U.S. Sen. Joe Lieberman filed papers Monday that will allow him to petition his way onto the November ballot if he loses the primary election, his campaign said.

The three-term Democratic senator faces a tough Aug. 8 primary challenge from businessman Ned Lamont. Lieberman, whom fellow Democrats have criticized for his support of the Iraq war and a perceived closeness with President Bush, is popular among many unaffiliated and Republican voters in Connecticut.

He announced his intent last week to run independently should he lose the primary. He would have to file signatures the day after the primary.

He also filed papers Monday to create a new party called Connecticut for Lieberman. A group of 25 people who are helping him form the party will oversee the petition drive, said Marion Steinfels, campaign spokeswoman.

Tom Swan, Lamont's campaign manager, has said an independent run would hurt Democrats.

"He does this from a position of weakness, where he looks like a desperate career politician attempting to cling to power," Swan said.

Lieberman was the Democratic Party's vice presidential nominee in 2000 and ran for the presidential nomination in 2004.