Obamacare repeal architect Tom MacArthur defeated by former Obama adviser

Andy Kim, a former national security adviser under President Obama, has defeated incumbent Republican Rep. Tom MacArthur, an ally of President Trump, in the last contested House race in New Jersey.

MacArthur, a two-term incumbent in the Garden State's 3rd congressional district, was a key figure in the Republican effort to repeal Obamacare -- and was the only New Jersey lawmaker to vote for the Republican tax cut bill, which hit taxpayers in affluent Northeastern suburbs especially hard.Â

The 36-year-old Kim declared victory shortly after Election Day, but the race remained officially too close to call until paper ballot counting was completed earlier this week. MacArthur conceded defeat on Wednesday, with Kim holding a 3,500-vote lead. More than 300,000 people voted in the race.

MacArthur's defeat means that Rep. Chris Smith will the only Republican congressman representing New Jersey next year. All 11 other House seats in the state will be held by Democrats. MacArthur's seat, in a wealthy and predominantly white swath of central New Jersey, was long considered safe Republican turf, and had only elected one Democrat since the early 1990s. Donald Trump carried the district by 6 percent in 2016, although Barack Obama had carried it in 2008 and 2012.

MacArthur is best known for the “MacArthur Amendment,” which would have let states obtain waivers that allowed insurance companies to charge some people, including those with pre-existing conditions, higher rates for health care. His amendment revived the Republican effort to repeal Obamacare, which ultimately died in the Senate with the legendary thumbs-down moment from the late Sen. John McCain.