John Anderson, originally a Republican, ran as an Independent in 1980. A ten-term congressman from Illinois (1961 through 1981). He was very critical of the Vietnam War, and President Richard Nixon during Watergate. In 1979, he joined a crowded field of republicans.
Unlike the other candidates, he said lowering taxes, increasing defense spending, and balancing the budget were an impossible combination, which earned him a lot of TV coverage and the national spotlight. After a contentious Fall, he opted to become an Independent, third-party candidate.
Anderson was much more popular across the country with all voters than he was in the Republican primary states. Without any campaigning, he was running at 22% nationally in a three-way race.
President Jimmy Carter, suspecting that Anderson's candidacy hurt him more than it did the republican nominee Ronald Reagan, refused to appear on stage with Anderson and sat out a major debate. But, Carter was wrong and, as Anderson's popularity faded, his supporters went to Reagan.
Ultimately, Anderson got 8% of the vote. Reagan got 47% and Carter got 44%.