The U.S. Chamber of Commerce has purchased a fourth round of television advertising for former Gov. Linda Lingle’s Republican campaign for U.S. Senate, bringing the business group’s investment in Hawaii to more than $1 million.

The $311,000 ad buy focuses on job growth and describes Lingle as an independent who would be a bipartisan leader in the Senate. Lingle has raised more money for her campaign than U.S. Rep. Mazie Hirono, her Democratic opponent, and the chamber’s presence in Hawaii has helped the former governor expand on that fundraising advantage.

“Linda Lingle has a proven record as a bipartisan leader who will work with members of both parties to get things done and create jobs,” Rob Engstrom, the U.S. Chamber’s senior vice president and national political director, said in a statement. “She stands with Hawaii’s job creators and will support free enterprise policies that create economic growth. Her independent leadership will serve Hawaii well in the Senate.”

Lingle raised more than $4.4 million before the August primary, while Hirono raised more than $3.5 million.

Interest groups that support Hirono have purchased ads on the congresswoman’s behalf, but not to the extent the chamber has helped Lingle.

Working Families for Hawaii, a labor group financed by the American Federation of State, County and Municipal Employees, upped its ad buy critical of Lingle this week by $14,600, for a total of $78,550 so far in the general election. (Working Families had spent more than $69,000 on behalf of Hirono during the primary.) Women Vote!, the independent expenditure arm of EMILY’s List, has spent $75,000 on ads targeting Lingle.

The ads from the labor and women’s groups highlight the teacher furloughs under Lingle as governor.

Seth Johnson, an assistant director in AFSCME’s political action department, said by telephone from Washington, D.C., that the ads are intended to remind parents and students about the disruption of furloughs.

“She’s trying to reinvent herself in this campaign,” Johnson said of Lingle’s bipartisan theme.

AFSCME is the national parent of local public-sector labor unions such as the Hawaii Government Employees Association.