For the second time in four months, the U.S. Chamber of Commerce has bought television ad time in Hawaii to support former Republican Gov. Linda Lingle’s run for U.S. Senate.

The ads are part of a nationwide campaign announced Wednesday by the Republican-leaning business interest group targeting four Senate races. The Chamber also was backing candidates in 17 U.S. House races.

"The Chamber is engaging more aggressively than ever to educate the public about the leaders who stand up for free enterprise and those who support big government policies," Thomas J. Donohue, president and chief executive officer of the U.S. Chamber, said in a statement.

Lingle, in a news release, also said she was informed Wednesday she would be receiving the group’s formal endorsement and that she was "pleased the U.S. Chamber has backed up their endorsement with a television schedule that reinforces my bipartisan position on growing our local economy."

In its latest 30-second Hawaii ad spot, the Chamber highlights Lingle’s stance on plans to promote tourism to create jobs and her ability to work in a bipartisan manner.

"Gov. Lingle believes in a bipartisan plan for increasing tourism — working across the aisle with President Obama finding solutions to boost our local economy for more opportunity," the ad narrator says. "She understands tourism will create jobs for Hawaii."

The latest two-week ad buy, beginning today, cost a reported $275,000, according to a source. There was no immediate response Wednesday to an email to the Chamber’s headquarters in Washington, D.C.

The Chamber spent $250,000 for a two-week ad buy in February, according to filings with the Federal Election Commission. The ads were classified as an independent expenditure, which are not coordinated with a campaign but can focus on issues that benefit a candidate.

Lingle is running in the Republican primary against former state lawmaker and former pilot John Carroll. U.S. Rep. Mazie Hirono and former U.S. Rep. Ed Case face off on the Democrats’ side. All are seeking the Senate seat being vacated by Sen. Daniel Akaka, who is retiring.

"The U.S. Chamber’s latest ad buy comes on top of the $250,000 they spent for Lingle in February, bringing their total spending to more than half a million already — and they’re only getting started," Hirono campaign manager Betsy Lin said in a fundraising appeal to supporters. "Why is the Chamber spending so much, so soon? Because they want Hawaii voters to forget the truth about Linda Lingle."

Lingle leads all challengers with $3.1 million raised overall for her campaign. Hirono is next with $2.5 million overall.

The $525,000 the Chamber has spent indicates the national interest Hawaii’s race is expected to attract as Democrats seek to maintain slim control of the Senate.

Nationally, the Chamber would not say how much it plans to spend in the latest round of advertising. Ad buys earlier this year in eight Senate races and 12 House races were estimated at $10 million. The Chamber only confirmed that the ad buy was worth eight figures and was unprecedented in the group’s 100-year history.

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The Associated Press contributed to this report.