So why do I still think Sanders is a factional candidate? He hasn’t made any inroads with non-white voters — in particular black voters, a crucial wing of the Democratic coalition and whose support was a big part of President Obama’s toppling of Clinton in the 2008 primary. Not only are African-Americans the majority of Democratic voters in the South Carolina primary (a crucial early contest), they make up somewhere between 19 percent and 24 percent of Democrats nationwide. In the past two YouGov polls, Sanders has averaged just 5 percent with black voters. Ipsos’s weekly tracking poll has him at an average of only 7 percent over the past two weeks. Fox News (the only live-interview pollster to publish results among non-white voters in July and August) had Clinton leading Sanders 62-10 among non-white Democrats in mid-July and 65-14 in mid-August. Clinton’s edge with non-whites held even as Sanders cut her overall lead from 40 percentage points to 19.

There are other indications that Sanders is unlikely to win the nomination. He hasn’t won a single endorsement from a governor, senator or member of the U.S. House of Representatives (unlike Obama at this point in the 2008 campaign). Sanders is also well behind in the money race (again, unlike Obama). These indicators haven’t changed over the past month.

But even if you put aside those metrics, Sanders is running into the problem that other insurgent Democrats have in past election cycles. You can win Iowa relying mostly on white liberals. You can win New Hampshire. But as Gary Hart and Bill Bradley learned, you can’t win a Democratic nomination without substantial support from African-Americans.