Class and age shaped the gender gap in Iowa. That gap was modest: Clinton last night won 50 percent of women and 44 percent of men. That almost exactly matched her total in the cumulative 2008 results against Obama, when gender was also somewhat muted: In that race Clinton carried 52 percent of women and 43 percent of men.

Clinton benefits from that pattern because women cast most of the Democratic votes (57 percent in all the primaries last time, the same number as in Iowa last night). And her overall advantage among women could rise as African American women, who usually vote more heavily than black men, weigh in. But in Iowa, Sanders signaled he could remain competitive enough among women (particularly younger woman) to prevent Clinton’s advantage there from becoming insurmountable.

It’s yet to be seen whether Clinton’s performance with blue-collar whites eroded because those voters are responding to Sanders’s full-throated economic populism—or simply because she’s not running again against an African American with an Ivy League pedigree. But, either way, if Sanders can sustain the competitive showing among blue-collar whites he displayed in Iowa, he can contest metal-bending Rust Belt states (like Ohio, Michigan, and Wisconsin) that previous wine-track candidates could only rarely threaten.

But to win those states—and the other big racially-diverse states that will almost certainly decide the Democratic race—Sanders must answer two other questions Iowa did not resolve.

The first is whether he can win minority voters. Minorities comprised only 9 percent of the voters in Iowa last night (up just slightly from 2008), but they will likely cast between 35 to 40 percent of the total vote in the 2016 Democratic primaries. As I noted on Monday, minorities are especially plentiful in the big states that will award the most delegates, including New York (where minorities cast just under one-third of the 2008 vote), Florida (about one-third), Virginia and New Jersey (about two-fifths), Illinois (over two-fifths) California (nearly half) and Georgia and Texas (over half).

The sample in Iowa was small, but Sanders won only about one-third of non-white voters there, compared to about three-fifths for Clinton. She polls even better among minorities in most national surveys. The next contest in New Hampshire, whose Democratic electorate in 2008 was 95 percent white, won’t provide much guidance on whether Sanders can shatter that wall. The real signals will come later in February from Nevada (where Hispanics and blacks each cast about one-sixth of the 2008 vote) and South Carolina (where African Americans cast a 55 percent majority of the 2008 vote).

Because of Clinton’s continued strength with white women, Sanders almost certainly can’t amass margins large enough among all whites to win big states if he can’t make further gains among minorities. Sanders’s campaign sees more opportunities with Hispanics than African Americans. But from whatever camp they’re drawn, winning more minorities in the big states looming on the calendar is the first key test of whether Sanders can truly threaten Clinton.