Republican Sen. Mark Kirk appeared to question his Democratic opponent's ties to the United States based on her biracial heritage at a debate on Thursday night in Springfield, Illinois.
Interested in Elections?Add Elections as an interest to stay up to date on the latest Elections news, video, and analysis from ABC News.
"My family has served this country going back to the Revolution. I am a Daughter of the American Revolution. I've bled for this nation," said U.S. Rep. Tammy Duckworth, Kirk's Democratic challenger in the Illinois Senate race.
In the 30-second time slot given to him for rebuttal, Kirk kept his remarks to just one sentence.
"I'd forgotten your parents came all of the way from Thailand to serve George Washington," the senator said, looking directly at Duckworth.
Duckworth, a former Army National Guard pilot and Iraq War veteran, was born in Bangkok to a Thai mom and American father who served in the U.S. Marine Corps. She is also a decorated war veteran who lost both her legs in 2005 in Iraq when the helicopter she was flying was struck by a rocket-propelled grenade. She became the first Asian-American congresswoman from Illinois after being elected to the U.S. House of Representatives in 2012.
Thursday's exchange quickly got national attention, with media outlets from around the country publishing the remarks. The Democratic Senatorial Campaign Committee sent out a statement calling Kirk's comments "offensive, wrong and racist."
The race is seen as critical for Republicans, who are struggling to hold on to enough seats to keep their Senate majority after the November election. Recent polling conducted by Southern Illinois University puts Duckworth ahead by 14 percentage points. Previous polls showed Duckworth with a slight lead.
Kirk sent out a flurry of post-debate tweets, one of which called Duckworth "one of the least effective members of Congress."
Duckworth tweeted a photo of herself with her parents and wrote, "my dad and his family have served this nation in uniform since the Revolution."