ST. PAUL — After two years marked largely by disappointment, lawmakers and health care experts are warily eyeing Minnesota’s health insurance exchange as it nears its toughest test yet.

The federal money MNsure has leaned heavily on will be gone by the end of the year, and it will have to keep afloat from the fees it pulls in from private plan signups. Health care consultants and academics say it’s too early to declare MNsure and other state-run exchanges unsustainable, but they see troubling signs.