Significant spikes in premiums, insurer dropouts and persistently low enrollment numbers are combining to make this fall’s sign-up period a crossroads for the Obama administration’s signature health law. Federal officials characterize the turbulence as temporary. At the same time, the administration is making a push in its final months to shore up the law by trying to sign up healthy people who are critical to the law’s sustainability but have so far rejected insurance. That push will take place against a backdrop of elections that will shape the law’s future.

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