The first was J. Strom Thurmond, then serving as governor of South Carolina as a Democrat. His amazing longevity is evidenced by the fact that he was still in public office six years ago. Thurmond became a senator in 1954, and switched to the Republican Party in 1964. When he left the Senate in 2003, he held the record for the longest tenure in that body, since surpassed by Robert Byrd.
Some background to the Thurmond presidential candidacy: Franklin Roosevelt's four landslide presidential victories between 1932 and 1944 were based on a large but volatile coalition. One element was southern segregationists, whose positions on other issues ranged from populist to conservative. The other element consisted of liberals, largely outside the southeast, with heavy support from organized labor, whose economic and political influence was still on the rise.
It's generally presumed that Roosevelt's sympathies would have been in favor of racial equality, but in practice he was very cautious on that set of issues, which enabled him to hold that coalition together. After 1945, which saw both Roosevelt's death and the end of World War II, the coalition became more difficult to sustain.
As I noted here, Truman moved decisively to integrate the armed forces in 1948. The party platform adopted by the 1948 Democratic National Convention included the following:
The Democratic Party is responsible for the great civil rights gains made in recent years in eliminating unfair and illegal discrimination based on race, creed or color. The Democratic Party commits itself to continuing its efforts to eradicate all racial, religious and economic discrimination. We again state our belief that racial and religious minorities must have the right to live, the right to work, the right to vote, the full and equal protection of the laws, on a basis of equality with all citizens as guaranteed by the Constitution. We highly commend President Harry S. Truman for his courageous stand on the issue of civil rights.
As a result, a large bloc of southerners ostentatiously walked out of that convention. (The conventions were televised that year for the first time, albeit to a small audience, so that heightened the drama.) They met separately, and nominated Thurmond for president on the States' Rights Democratic ticket, but they were more popularly known as the Dixiecrats.
An emerging star of the Democratic Party made a major speech in favor of the civil rights plank in the platform at their 1948 convention. The mayor of Minneapolis, who was a U.S. Senate candidate that year, said:
To those who say that this civil-rights program is an infringement on states’ rights, I say this: The time has arrived in America for the Democratic party to get out of the shadow of states' rights and to walk forthrightly into the bright sunshine of human rights.
That mayor was Hubert Humphrey, who went on to represent Minnesota in the Senate for a total of 23 years in two separate periods, and to serve one term as vice president. Perhaps one could compare that speech to Barack Obama's keynote address at the 2004 Democratic National Convention, as another forum for a new U.S. Senate candidate to be introduced to a national audience. Later this year, we will know whether Obama gets any closer to the White House than did Humphrey.
Reverberations from Thurmond's 1948 candidacy continued to be felt for many years. Trent Lott, Republican of Mississippi, was pressured to resign his position as Senate Republican leader in 2002, after publicly stating that the U.S. would have been better off, had Thurmond won in 1948. Thurmond changed with the times, abandoned his segregationist positions, and won respect as an elder statesman. Thus, it was to be expected that a Republican leader would praise him as he was nearing retirement, but to praise the Dixiecrat platform, which Lott's remarks could be intepreted as doing, was by 2002 unacceptable.
More to come on the other third-party candidate, and the 1948 result.