What is Po-tay-to Po-tah-to?
1.
Actually, Ira Gershwin lyrics, from song collaboratively written with his brother, George, titled Let's Call the Whole Thing Off. First performed by Fred Adstaire (with Ginger Rogers) in 1930s film, Shall We Dance. Originally, "You think this way, I think that way, this'll never work." Has evolved into, "You think like this, I think like that, means the same, whatever...". Now somewhat akin to "six of one, half-dozen of the other".
A: "I'm going to the park to use the walking trail."
B: "Oh, the bike path, you mean?"
A: "Potayo, potahto."
2.
Taken from the Louis Armstrong Lyrics to "Let's Call The Whole Thing Off":
"You like potato and I like potahto, You like tomato and I like tomahto
Potato, potahto, Tomato, tomahto, Let's call the whole thing off."
Used by somebody comparing two things that are essentially interchangeable or two words for the same thing.
Republicans - Right-wing crooks. Po-tay-to po-tah-to.