WASHINGTON — Democratic Senator Inouye said yesterday that he is supporting Ned Lamont over Senator Lieberman because of the Connecticut lawmaker’s contention that the Democratic Party does not stand for mainstream America.

Mr. Inouye, who campaigned in Connecticut for Mr. Lieberman prior to the August 8 primary, issued a statement endorsing Mr. Lamont and citing Mr. Lieberman’s recent criticism of the party. Mr. Lamont upset Mr. Lieberman in the Democratic primary, and the three-term senator is running as an independent in hopes of holding his seat.

“After the primary, Senator Inouye was most disappointed and unhappy when Senator Lieberman remarked that the Democratic Party no longer represented the mainstream of America and that the Democratic Party had lost its values,” the eight-term Hawaii senator said in the statement.

Mr. Inouye is the latest prominent Democrat to rally behind Mr. Lamont, a political newcomer whose anti-war views helped him topple Mr. Lieberman, a staunch supporter of the war.

Party officials such as Senator Reid of Nevada, the Senate Democratic leader, who backed Mr. Lieberman in the primary, have endorsed Mr. Lamont in the three-way race. Republican Alan Schlesinger also is seeking the Senate seat. The Connecticut race has been cast by many as a referendum on President Bush’s Iraq war policies. Mr. Lieberman has been a strong supporter of Mr. Bush’s handling of Iraq, winning endorsements from Republicans.

Meanwhile, a Republican former congressman and U.S. housing secretary, Jack Kemp, will hit the campaign trail with Mr. Lieberman.