As much as I despise Franklin Roosevelt and his policies, I have to give him credit for dumping Wallace in '44. FDR knew he was in poor health, and must have been mightily uncomfortable envisioning Wallace as the next president.
Roosevelt had the smarts to replace Wallace on the '44 ticket with Harry S Truman, a man who he (FDR) was only vaguely aware of, but a man who had proven his ability insofar as administrating policy and understanding the workings of government.
The selection of Truman is IMHO FDR's legacy. Truman was an honest no-nonsense democrat Senator who had been an artillery officer during WWI, and as such he harbored no illusions with regard to the USSR and its inclinations. He also understood the Japanese, their military discline, and their unwillingness to capitulate under any terms. That understanding was the source of his decision to use nuclear arms on Japan, a couragous act which goes unrecognized to this day by many misguided idiots.
The years immediately following WWII were critical in checking the aspirations of Stalin mentioned in this article. It was damned fortunate for the US that Harry Truman, and not Henry Wallace, sat in the Oval Office during the opening days of the Cold War.
I rank Truman as the second greatest president of the 20th century. First place goes to Theodore Roosevelt and third place goes to Ronald Reagan.
When he was president he actively aided Lyndon Johnson in stealing a Senate seat.