From what I know, Li'l Gideon represents Trump, where he had white hair and seen in a suit. He is a fraud, a metaphor of Trump who uses lies to manipulate people, especially whites to support him.
The Pines represents the Democratic party. Mabel herself serves Clinton. At the beginning of the series, we see Mabel and Li'l Gideon dating, eventually breaking up. The break-up is a metaphor to Trump and Clinton announcing their presidential run.
Dipper represents Tim Kaine; Grunkle Pines represents Sanders, and Ford Pines represents Former Mayor Mike Bloomberg. Bill Cipher himself represents Mike Paine early in the series and later Wikileaks founder Jullian Assange.