Embattled GOP Sen. Mark KirkMark Steven KirkDuckworth announces reelection bid Brave new world: Why we need a Senate Human Rights Commission  Senate majority battle snags Biden Cabinet hopefuls MORE (Ill.) appeared to question his opponent's heritage during a debate Thursday night. 

Asked about their long-term plan for American influence in the Middle East, Rep. Tammy Duckworth (D), who is Asian-American, said her family "has served this nation in uniform going back to the Revolution." 
 
"I am a daughter of the American Revolution," she added. "I have bled for this nation." 
 
Kirk — considered the most vulnerable GOP senator up for reelection — replied: "I forgot that your parents came all the way from Thailand to serve George Washington." 
 
Duckworth was born in Bangkok. Her mother is an immigrant and her father is a World War II veteran. 
 
The Democratic congresswoman didn't initially respond to Kirk's remark, but asked by the debate moderator if she wanted to comment, she touted both sides of her family. 
 
"There's been members of my family serving in uniform on my father's side going back to the Revolution," she said. "I'm proud of both my father's side and my mother, who is an immigrant." 
 
She later posted a photo of her and her parents on Twitter.
"Senator Kirk has consistently called Rep. Duckworth a war hero and honors her family's service to this country," Eleni Demertzis, a spokesperson for the Kirk campaign, said in a statement. "But that's not what this debate was about. Rep. Duckworth lied about her legal troubles, was unable to defend her failures at the VA and then falsely attacked Senator Kirk over his record on supporting gay rights."
 
Duckworth is a veteran of the Iraq War, where she lost both legs after a helicopter she was co-piloting was struck by a rocket-propelled grenade.
 
The Democratic Senatorial Campaign Committee quickly pounced on Kirk's comments. DSCC spokeswoman Lara Sisselman called the comments "offensive, wrong, and racist." 

"A struggling political campaign is no excuse for baseless and despicable attacks, and Senator Kirk owes Congresswoman Duckworth and her family an apology," she added. 

Kellyanne Conway, Republican presidential nominee Donald TrumpDonald TrumpBiden administration to keep Trump-era rule of turning away migrants during pandemic On The Money: Biden, Pelosi struggle with end of eviction ban | Trump attorney says he will fight release of tax returns Lack of transatlantic cooperation on trade threatens global climate change goals MORE's campaign manager, quickly weighed in on Twitter, asking if the story was about "the same Mark Kirk that unendorsed his party's presidential nominee and called him out in paid ads? Gotcha. Good luck."
 
Kirk touted as recently as Wednesday that he broke with the party's presidential nominee because Trump questioned the qualifications of a federal judge overseeing a case against Trump University because of his Mexican heritage.
 
The comments "showed me that he was so ignorant of the key aspect of Americanism that our president should know about," Kirk told a local radio station. 
 
Thursday night isn't the first time the GOP senator has made a controversial comment. He joked last year during a committee hearing that Sen. Lindsey GrahamLindsey Olin GrahamGraham's COVID-19 'breakthrough' case jolts Senate Graham says he has COVID-19 'breakthrough' infection Graham, Cuellar press Biden to name border czar MORE (R-S.C.), who is unmarried, is a "bro with no ho." 
 
He also came under criticism earlier this year when he compared President Obama to a "drug dealer in chief" over a $400 million payment to Iran. 
 
Kirk is facing an uphill battle to keep his Senate seat in the blue state next month. Duckworth is currently leading in the polls by an average of 7 percentage points, according to RealClearPolitics.