BANGOR (AP) — The U.S. Chamber of Commerce, which spent $400,000 on attack ads against independent Angus King, continued to criticize the former two-term governor at campaign stops Monday on behalf of Republican Charlie Summers, and its national political director suggested the Senate race is a key “battleground.”

The chamber’s Rob Engstrom said the race to succeed Sen. Olympia Snowe has made Maine a “top-tier race that’s going to decide the balance of power in the United States Senate.”

In stops in Bangor, Lewiston and Biddeford, Engstrom repeated many of the criticisms of King in the ad campaign that described King as “king of spending” and “king of mismanagement” and touted Summers as the “probusiness candidate” in a six-way race featuring a Republican, Democrat and four independents.

“We think voters here have a clear choice between the free enterprise system and more government solutions,” Engstrom said. “We need leaders in Washington who understand the private sector, who come from the private sector.”

Summers, for his part, said he wants to “get government out of the way, and there are those in this race who don’t.”

King responded by saying that he’s spent most of his life in the private sector and that he’s “very familiar with the issues facing business — both large and small.”

“Businesses across the state are still scratching their heads over the U.S. Chamber’s position. It just shows how out of touch Washington is with Maine,” King said.

Not all business owners support the U.S. Chamber.

Suzanne Kelly of Kelly Realty Management in Bangor, who’s a member of the Maine Small Business Coalition, said the U.S. Chamber doesn’t speak for all Maine businesses.

“It’s basically a conservative Super PAC representing big business and health insurance companies. What they support is often directly opposite of what’s most important to Maine small businesses,” she said.

King spent Tuesday campaigning in Skowhegan and Madison, visiting a New Balance manufacturing plant and called on the U.S. to suspend trade negotiations with Vietnam.

He said eliminating a trade tariff on Vietnam could have a devastating effect on New Balance, which employs 900 people in Maine. “To even contemplate — let alone actively negotiate — a step that would result in jobs being lost anywhere in the country in this fragile economy is simply unacceptable,” he said in a statement.