Now, the main reason for all this gloom was the mayor.

4 seconds sound clip from the Santa Claus Is Comin' to Town (1970) movie soundboard.

You can hear this line at 00:03:55.085 in the Blu-ray version of the movie.

Quote context

[...]

- So you want to know all about Santa, huh? Best place to start is at the very beginning, when Santa was just a little baby.

- You mean Santa was once a baby?

- Of course! Everybody's got to be a baby at least once in their lives.

- Now, this was years and years ago. Oh, way back.

- In one of the northern countries, there was a small city called Sombertown.

- It was a cold, cold place which shivered in the shadows of the strange Mountain of the Whispering Winds.

- Now, the main reason for all this gloom was the mayor.

- A mean old grouch of a fellow who was known as Burgermeister Meisterburger.

- Herr Burgermeister, Herr Burgermeister!

- Look what was discovered on your front stoop.

- What? What, Grimsley? The milk? The daily paper?

- No, sir. A baby!

- Oh, is that all?

[...]