The U.S. Chamber of Commerce, which has bought a series of positive television advertisements promoting former Gov. Linda Lingle’s Republican U.S. Senate campaign, is now going negative against U.S. Rep. Mazie Hirono, Lingle’s Democratic opponent.

The chamber has purchased $250,000 worth of advertising opposing Hirono, who leads Lingle in public-opinion polls. The chamber has also spent more than $6,650 on a get-out-the-vote video for Lingle.

The U.S. Chamber has invested more than $1.2 million overall in advertising in Hawaii to help Lingle, the most by any interest group in the Senate campaign. Several labor and women’s groups have bought ads critical of Lingle on behalf of Hirono.

The independent spending by the U.S. Chamber suggests that some on the mainland still view the Senate race as competitive.

"I’m very proud that the No. 1 business organization in the entire nation has focussed on my race as one they feel is important, because I have a background in supporting job creation," Lingle said during a debate with Hirono on Thursday.

Hirono said the U.S. Chamber’s advertising for Lingle is an attempt to "reform her image here."

The congresswoman said that the Supreme Court’s ruling in Citizens United v. Federal Election Commission in 2010, which allows unlimited independent political spending by corporations and labor unions, "truly warps" participatory democracy. She said she supports a constitutional amendment to overturn the ruling.