Source, in full
Ch. 9 "Rogers was a lifelong Democrat but he studiously avoided partisanship. He contributed to the Democratic campaign funds, but at the same time he frequently appeared on benefit programs to raise money for the Republican treasury. Republican leaders sought his counsel in their campaigns as often as did the Democrats." ~ P. J. O'Brien
Variants
I don't belong to an organized political party. I'm a Democrat.
I belong to no organized party. I am a Democrat.