I can think of several Republicans other than Trump who could have beaten Hillary. Unfortunately, they are all dead...Theodore Roosevelt, Dwight Eisenhower, Ronald Reagan.
I'm old enough ( even though I was a little kiddo back then )to remember his speeches and run against Stevenson.
Back then, EVERYONE praised Stevenson to the skies; he was THE "great orator". Then the book of his speeches came out and everyone couldn't believe that they were praising him, when they heard he say the words.
Unfortunately, I have a far too good memory and I remember that election cycle, as though it were yesterday. I also know what a damned wuss/GOPEer Ike REALLY was, as president.