Why doesn't setting ts=4 in .vimrc work?

Question

I have a stupid question but I am stuck. I do set set ts=4 in my .vimrc file, but it looks not work. Open a new file, tab is still extended as 3 spaces. And under command mode, "set ts" got a "tabstop=3". Is there a final file like .vimrc that overwrite my ts?

Even I type :set ts=4, in vim, when I type tab, it only has 3 spaces in length.

Here is my suspicious options that cause this annoying result in my .vimrc

set autoindent
set shiftwidth=4
set softtabstop=4
set backspace=2

Thanks.

Answer 1

Try this:

:verbose set tabstop?

in vim, it will tell you where the tabstop option value is coming from.