Basing on my Alternate Presidents post about it, (my opinion about) the fate of some important US politician in this scenario:
-Harry Truman (D-Missouri)
Senator Truman was a popular Democrat from Missouri. He opposed to Wallace renomination and main part of his foreign policy but refused to bolt in the new Conservative Party. In 1952 he was one of the many "Democratic" candidates, together with Pepper, Taylor, Douglas and McMahon. Although he was the first between Democrats he didn't carry any state. He continued to serve as Independent Senator from Missouri before retiring in 1966.
-Dwight David Eisenhower (R-New York)
A popular former General he served as President of Columbia University. After initially declined, he reluctantly accepted to be Dewey's Secretary of Defense in the midst of Yugislavian Crisis. After contrasts about US involvement in Indochina he retired in 1956, officially for health reasons, and spent his remaining life in his farm in Pennsylvania.
-John Fitzgerald Kennedy (D-Massachusetts)
The scion of a important political dynasty, JFK seemed destined to an important political office but after his defeat in the 1952 Senate race against Henry Cabot Lodge Jr and the Democratic collapsing he preferred to realized his dream and becoming a famous journalist. He won two Pulitzer, one for his coverage of Cuban War in 1962, the second for his interview to failed Presidential assassin Lee Harvey Oswald in 1963. He married actress Marylyn Monroe the next year and in 1981 he replaced Walter Cronkite as main anchorman of CBS. His brother Bobby briefly flirted with Conservatives when he served as counselor of Joe McCarthy but never joined due their racist ideology: instead he was one of the most famous lawyer, famous for his civil rights cases. In 1966 he accepted Progressive nomination to become Senator of Massachusetts and was narrowly elected, serving until 1972 when he was assassinated by Arthur Bremer while he was running for Progressive nomination, then won by his supporter George McGovern.
-Lyndon Baines Johnson (D-Texas)
Johnson, a main kingmaker, was defeated in 1948 Senate primary against more conservative Coke Stevenson. After that, he became a successful businessman. In 1954 he did a comeback as Conservative and won his old House seat. Thanks to Richard Russell and John Connolly's support, he was chosen as House Whip, leading conservative battles in the House but mantaining his good relationships with everyone. In 1964 he became House Speaker when Conservatives took the Congress for the first time. He strongly supported the Goldwater and defended him from impeachment attempts after his using nuclear weapons in Indochina. He returned Whip after conservative defeat in 1966 and stayed in this role until his death in 1974.
-Gerald Rudolph Ford (R-Michigan)
Ford reached his dream, becoming Speaker of the House in 1966 and staying as that until retirement in 1986, when he was succeeded by Edward Madigan.
-James Earl Carter (D-Georgia)
Jimmy Carter was a young pro-segregation republican activist when he defeated Rapresentative Bo Callaway in 1966. Carter served as Congressman between 1966 and 1980 and was considered a main candidate to succeed Ford as Speaker but instead he decided to run for Senate, defeating Herman Talmadge. He tried a failed primary run in 1988, losing against Joe Biden. Actually he is the oldest US Senator and, as most senior Republican in the Senate, he is the current President Pro Tempore of the Senate.
-Ronald Wilson Reagan (R-California)
Reagan was a popular actor and a Conservative Rapresentative before be nominated as Secretary of State in Goldwater Administration. After infamously defending in UN the nuclear attacks in Vietnam, he was the Conservative candidate in 1976 but lost against fellow Californian Richard Nixon. He became Secretary of State again in Buckley Administration, becoming famous for some noted expressions, and retired in 1989, battling Alzheimer in his last years.
-William Jefferson Clinton (D-Arkansas)
Clinton was a young Republican Governor of Arkansas and was a candidate for Republicab nomination in 1988, losing to Joe Biden. He was considered a frontrunner for 1996 nomination but he declined candidacy after a series of sex and financial scandals. Acquitted and divorcee from Hillary, he actually run a alimentary charity in Little Rock.
-George Walker Bush (R-Texas)
George Jr tried to start a own political career but failed. He became National Baseball League Chairman and actually run sports charity. His brother Jeb lost against Biden and Romney in 2012 and 2020 and actually is the Secretary of Commerce in Romney Administration.
-Barack Hussein Obama (D-Illinois)
Obama was elected as Republican in 2002 and served as Congressman until 2010, when he run and won to become Illinois Governor. He was considered a main candidate for 2020 but instead he decided to stand for Senate in 2018. Currently he is the main sponsor of Romneycare in the Congress.