Senator Mark Kirk apologized Friday after he made a racist remark against Representative Tammy Duckworth at a televised debate on Thursday.

In the exchange, Duckworth answered a question by highlighting her and her family’s history of commitment to military service, including ancestors who had served during the American Revolutionary War. Kirk responded with the derisive and racially charged quip: “I had forgotten that your parents came all the way from Thailand to serve George Washington.”

Duckworth is a biracial Asian American whose father’s family has lived on American soil since before the nation’s founding. Her mother is Chinese Thai. Duckworth was born in Bangkok, Thailand and spent her childhood living throughout Southeast Asia in relation to her father’s military service before the family relocated to Hawaii when Duckworth was sixteen. As an adult, Duckworth served nearly eighteen years in the US Army Reserve and he Illinois Army National Guard as a helicopter pilot, and lost both her legs while deployed to Iraq in 2004, becoming the war’s first female double amputee. Upon returning states-side, Duckworth entered public service to become a vocal advocate of veterans’ rights.

Kirk’s remark draws upon the Perpetual Foreigner stereotype of Asian Americans to dismiss Duckworth’s personal and familial military history. Duckworth’s family has been American for about as long as there were such things as Americans, and yet Kirk reads Duckworth’s Asian features and sees someone foreign, alien, and unwelcome.

The Perpetual Foreigner stereotype has long been used to rationalize profound mistreatment of Asian Americans. In fact, for most of our history, laws that prohibited immigration and naturalization of Asians based on race formed the basis of decades of legal and cultural discrimination and disenfranchisement. For Kirk to cast Duckworth — who has given so much of herself to military and civil service of America — as un-American because of her race is a racist remark that hurts and offends not just Duckworth, but all Asian Americans.

Kirk’s remark also touches upon stereotypes that specifically impact people of mixed race heritage, who often find their multiracial identity dismissed or erased by those who assume them to be only of one race. Often, multiracial people endure words and actions committed by people who police racial boundaries by presuming the right to flatten away the complexities of a mixed race person’s own identity.

Republicans running in down-ticket races this year have felt the reverberations of Donald Trump’s disgusting racism and xenophobia. America’a Political Right is quick becoming the party of intolerance, racism and anti-pluralism. Kirk’s remark does little to challenge this trend.

Kirk issued a terse Twitter apology to Duckworth over Twitter on Friday afternoon.

Sincere apologies to an American hero, Tammy Duckworth, and gratitude for her family's service. #ilsen — Mark Kirk (@MarkKirk) October 28, 2016

Duckworth is running to unseat Kirk as Illinois’ junior senator. Recent polls show that Duckworth is leading Kirk by as many as seven points. If elected, Duckworth would be the first Asian American to serve as Senator of Illinois, and only the second Asian American woman to be elected to the US Senate.