MADISON, Wis. (AP) — The Sept. 11 terrorist attacks have suddenly become a major issue in Wisconsin’s surprisingly tight U.S. Senate race.

Tommy Thompson invoked Sept. 11 in a statewide television advertisement on Tuesday, attacking Democratic challenger Tammy Baldwin for voting against a 2006 resolution honoring victims of the attacks.

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Baldwin responded with her own spot Wednesday, saying Thompson personally profited from the attacks by making $3 million from a health care firm that scored a government contract to treat first responders.

The pair of hard-hitting ads on such an emotional topic is the product of an unexpectedly tight contest, one of a series of Senate race stalemates across the country that have left open the question of which party controls the chamber come January. With fewer than two weeks left before Election Day, campaigns in stubbornly close races_from Nevada to New England_are pouring their creativity and campaign cash into getting voters’ attention and gaining a lead.

Republicans must gain four seats if President Barack Obama is reelected, or three if Republican hopeful Mitt Romney prevails, to win the majority of the 100-seat seat Senate.

The “Tommy vs. Tammy” race in Wisconsin is the most expensive Senate contest in the state’s history_and one of the nation’s costliest_with spending from the candidates and outside groups topping $42 million.

Thompson does not appear in his 9/11 ad. Instead, three veterans speak directly to the camera about Baldwin’s vote as a member of Congress against the 2006 resolution.

“It is a slap in the face to every one of their families and anyone who has ever served in the United States military,” Ron Amato, identified as a retired member of the U.S. Navy, says in the ad. “Tammy Baldwin’s extreme, far left approach leaves this country in jeopardy.”

Baldwin’s response ad opens with a narrator calling Thompson’s ad a “disgrace” and concludes: “Tommy Thompson should be ashamed.”

John Kraus, Baldwin’s campaign spokesman, called Thompson’s ad a sign of desperation.

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“I think it is the tipping point for Tommy Thompson’s desperate campaign,” Kraus said. “Wisconsin voters are smart enough to see this for what it is, which is it’s dishonest, it’s disgusting. The real question is whether Tommy Thompson is going to take responsibility for this ad and his record.”

Thompson’s campaign spokeswoman Lisa Boothe issued a statement standing by the ad and defending Thompson’s record both as U.S. health secretary during the attacks and afterward when led a Wisconsin company that scored an $11 million government contract to treat first responders.

“Tommy Thompson has always honored the victims of Sept. 11 and the first responders who worked tirelessly to save so many lives that horrific day,” Boothe said. “From the moment our nation was attacked, Thompson committed himself to providing the health care that was needed for victims and first responders.”

Baldwin, in office since 1999, voted for nine resolutions honored victims of the attacks. She was one of 22 Democrats who voted against the 2006 resolution because it also contained endorsements of Republican policies she voted against, including immigration reform and the Patriot Act.

“The Republicans show enormous disrespect to the 9/11 victims and families by playing election year politics with something as solemn as the fifth anniversary of 9/11,” she said in 2006.

The Baldwin campaign’s ad points out that Thompson, after serving four years as U.S. health secretary under George W. Bush, worked as president of Logistics Health, Inc. The Wisconsin-based company won an $11 million government contract in 2008 to treat 9/11 emergency responders but was roundly criticized for being slow to provide benefits and help those suffering from health issues related to their work at the scenes of the attacks.

Thompson made $3 million when Logistics Health was sold last year. The Baldwin ad alleges that Thompson profited off the company’s 9/11 contract.

Mahlon Mitchell, a Baldwin supporter and president of the Wisconsin Fire Fighters Association, said he was shocked by Thompson’s ad making the attacks an issue in the race.

“It irritates the hell out of me when people try to politicize 9/11,” Mitchell said.

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