Well, not a great topic, I must acknowledge myself.
But, as I've thought about it a bit, I didn't want to have wasted entirely my time.
At least, our posting machine, our "What-If-Man", aka Kalwejt, may be interested
So, in 1944, after FDR has been again reelected, after Hitler has won the battle of the Bulge, postponing the end of WW2 and after Japan's surprise offensive in the Russian Far East has forced Stalin to stall his troops in Europe,
a wide consensus in the United States leads to the need for amending the Constitution and give FDR a mandate for life !
VPs are chosen at will by presidents, who are obliged to confirm or change them at least every 4 years.
Of course, this first presidency for life doesn't last for long... Truman replaces him, BUT VPs replacing presidents must organize an election in the next 6 months: they don't become presidents for life.
So, 2 possibilities:
Harry Truman 1945-1972 (acting president, wins 1945 election)
Edmund Muskie 1972-1973 (acting president, loses 1973 election)
Richard Nixon 1973-1974 (wins 1973 election, resigns)
Gerald Ford 1974-2006 (acting president, wins 1975 election)
Jeb Bush 2006-2007 (acting president, loses 2007 election)
Mark Warner 2007-... (wins 2007 election)
Harry Truman 1945 (acting president, loses 1945 election)
Thomas Dewey 1945-1971 (wins 1945 election)
Richard Nixon 1971-1974 (acting president, wins 1971 election, resigns)
Gerald Ford 1974-1975 (acting president, loses 1975 election)
Edmund Muskie 1975-1996 (wins 1975 election)
Albert Gore 1996 (acting president, loses 1996 election)
Jack Kemp 1996-2009 (wins 1996 election)
Mitt Romney 2009-... (acting president, elections set on next September...)
Sorry to Clintonistas, Gore supporters, Reagan fans, fond of Ike, mads of Kennedys....
Death is an unpredictable event, that's what is "funny" in this case...