I personally cannot support Schweitzer for his record (or lack thereof) on gay rights. I want to support the first president who's unapologetically pro-marriage equality in the next election. Democrats have beat around the issue for too long.
I wouldn't say he's moderate. Sure, he loves guns and comes from a very conservative background (rancher in rural Montana), but he supports single-payer health care, supports legal medicinal marijuana, and wanted Bush to pull Montana's National Guard out of Iraq to deal with Montana's wildfires at the time. He's more of a left-libertarian.
This is actually why I wouldn't mind having him as a nominee or president. There's just that lingering issue.