Tucker Carlson has walked away from the Republican Party and is talking up a new third party, a move that could split the right and unsettle GOP leaders.

• Carlson says he no longer fits in the GOP and wants a new political party.
• Critics point out he was a registered Democrat for 20 years, which he blames on needing DC access as a reporter.
• His past ties raise doubts about how sincere his shift really is.
• A third party built around him could pull voters away from Republicans.

Outlook: Expect more back-and-forth over Carlson's motives and whether a real third-party push takes shape before the next election.