A banner reading "Jobs" hangs on the facade of the US Chamber of Commerce in Washington on February 22, 2011.

Story highlights

The Chamber of Commerce will air ads on Senate races in New Hampshire, Wisconsin, Pennsylvania and Ohio

The chamber announced an eight-figure ad buy beginning Friday

New York CNN  — 

The U.S. Chamber of Commerce is wading into some of the most hotly contest Senate races this year, supporting Republicans and hammering Democrats over Obamacare and spending.

In what the group said will be the first in a series of campaigns, the chamber announced an eight-figure ad buy beginning Friday in Ohio and New Hampshire. The ad campaigns, which will run through July, will continue in Pennsylvania and Wisconsin in the coming weeks.

“We’re laser-focused on our mission, and it all comes down to preserving a pro-business majority in the U.S. Senate and governing,” Chamber of Commerce national political director Rob Engstrom said in a statement.

The group authorized $3.6 million in expenditures on Friday, according to federal election records. Asked about a precise total figure that the group plans to spend, Erica Flint, a spokeswoman for the chamber, would only say, “It is an eight-figure buy, but we don’t discuss specifics associated with our buys.”

For some Democrats, including former Ohio Gov. Ted Strickland, Russ Feingold in Wisconsin and Katie McGinty in Pennsylvania, those attacks will center around their support for the Affordable Care Act.

The chamber said its ad in New Hampshire will criticize Gov. Maggie Hassan, who is running against Republican Sen. Kelly Ayotte, “for her profligate spending in the state legislature and governor’s mansion.”

In Ohio, the group intends to contrast Strickland’s work to expand Obamacare with Republican Sen. Rob Portman’s opposition to the health care law.

Republican Wisconsin Sen. Ron Johnson is in a tough fight with Feingold, the man he defeated in 2010. The chamber’s ad paints Feingold as a career politician who has worked to “expand government through increased taxes, spending and Obamacare.”

The ad aimed at McGinty will focus on her “hyper-partisan record and extreme commentary on issues like Obamacare.”

CNN’s Theodore Schleifer contributed to this report.