Is the question, "Could the Democrats have won the 1952 Presidential Election?" Or is the question, "Could the Democrats have defeated Dwight Eisenhower in 1952?".
I don't believe that any Democrat could have beaten Eisenhower, especially after Nixon dodged the issue of his slush fund. Had a Democrat like Sen. John Sparkman (D-AL) or even Sen Estes Kefauver (D-TN) led the ticket, they MIGHT have carried the entire South, but that didn't happen. Adlai Stevenson was a candidate the Democratic Establishment came up with, and I'm not convinced he was the strongest candidate the Democrats could have come up with.
But what if Eisenhower had not been nominated? What if the GOP nominated a Taft-Warren ticket? After all, Eisenhower did NOT hava a majority after the votes were counted on the 1st ballot; it was a number of ballot switches at the end of the 1st ballot that swung it to Eisenhower.
Sen. Robert Taft (R-OH) had a LOT of support in the GOP, and there was, even then, a strong number of Republicans that believed that a small government conservative like Taft was what much of America wanted. Warren was a favorite son, and the California delegation was kept in line by Nixon for Warren solely for the purpose of swinging the convention to Eisenhower, but Warren had been the VP pick in 1948 and had Presidential ambitions. The GOP would have gotten behind a Taft-Warren ticket. California's liberal and moderate Republicans would have swung to Taft for Warren, and California's conservative Republicans would have swung to Taft to be rid of Warren as Governor.
Let's consider this race: Taft/Warren vs. Barkley/Johnson (LBJ). How would THAT map have played out?
Barkley/Johnson (277) beats Taft-Warren (254) in the EC if EVERYTHING went right.