Dr Ronny Jackson, US President Donald Trump's previous White House doctor, was projected to win a seat in the House of Representatives, according to US media.
He was projected by NBC News and CNN to defeat Democratic candidate Gus Trujillo in Texas state's 13th Congressional District, a safe seat vacated by a fellow Republican.
Dr Jackson, who retired from the Navy as a rear-admiral the previous year, was first appointed to the White House Medical Unit under previous president George W. Bush. He then became the president's doctor in 2013, under Mr Barack Obama.
But he gained national fame after effusively praising Mr Trump's health and "great genes" in 2018, declaring: "I told the president that if he had a healthier diet over the last 20 years, he might live to be 200 years old."
Soon after, Mr Trump nominated him to lead the Department of Veterans Affairs, but Dr Jackson withdrew his name from consideration following allegations he improperly handed out drugs and was drunk at work.
During his campaign for Congress, Dr Jackson positioned himself as a supporter who is close to Mr Trump, backing the narrative that Mr Obama weaponised the government to spy on Mr Trump.
He also broke ranks with public health officials on the coronavirus, stating that mask wearing should be a "personal choice", and questioned Mr Joe Biden's cognitive capacity to run for president.