Some Republicans support Social Security privatization because they believe that forcing individuals to own stocks will turn them into Republican voters.
From a historical and theoretical perspective, it seems likely that widespread stock ownership is probably good for Republicans when stocks go up, as in the 1920s, and bad for Republicans, when they go down, as in the 1930s.
Marilyn Monroe offered some acute advice to Republican strategists looking to lure in voters with mandatory stock ownership in "Gentlemen Prefer Blondes:"
He's your guy when stocks are high,
But beware when they start to descend
It's then that those louses go back to their spouses
Diamonds are a girl's best friend.