Hillary Clinton’s surprise loss in Michigan on Tuesday night highlights her electoral vulnerabilities in the upcoming general election.

The Democratic presidential front-runner is struggling to attract young voters, exit polls showed.

She also is weak with white men, including blue-collar Rust Belt voters who will be coveted in the swing states of Pennsylvania, Ohio, Michigan and Wisconsin in November.

Looming even larger is an overall enthusiasm gap between her supporters and rival Bernie Sanders’s — and perhaps also those of GOP front-runner Donald Trump.

Clinton maintains a sizable delegate lead in the Democratic primary over Sanders; she ultimately took home more delegates than her rival on Tuesday night because of her big win in Mississippi.

But many Democrats—including her own allies — are worried about whether this will translate into victory or a defeat in the fall.