15. That's great until he starts losing you safe Democratic states.
You have to understand how big gun control is in Southern New England and the urban East Coast. Yes, Brian Schweitzer will win you votes in rural America. He's dead in the water and will never gain even a modicum of traction, even as the Democratic nominee, someplace like CT where there is a substantial single-issue vote pool for stronger gun control.
(You need to understand this. Many Nutmeggers would trade the signature accomplishments of the current Democratic administration for a repeal of the 2nd Amendment. Not a majority, but enough that a Republican like Chris Christie willing to discuss gun control would win CT against the likes of a NRA-friendly Democrat like Schweitzer solidly.)
You can't lose safe Democratic states to win Republican leaning states. There will never be a strong RKBA Democratic nominee because the Democratic breadbasket of the Northeast is made up of voters no more willing to compromise on guns than they are on abortion.