Backed by venture capitalists, including Josh Kushner, one of the company’s founders and the brother of Jared Kushner, President Trump’s son-in-law, Oscar has focused almost exclusively on selling insurance in the market created by the Affordable Care Act.

“We’re confident that when the dust settles, the market for health insurance will stabilize in time for 2018,” Mario Schlosser, the company’s chief executive, wrote in a blog post. “For all of the political noise, there are simply too many lives at stake for representatives in Washington, D.C., not to do what’s right for the people.”

Other insurers also appear to be gambling on the current market, in spite of the political turbulence. Molina Healthcare, another major player in the market that has expressed concerns about its stability, said it had filed initial proposals in all nine states where it has business, according to a company spokeswoman.

Medica, a small nonprofit insurer, said on Monday that it would offer plans statewide in Iowa, although it is seeking rate increases that average 43 percent. Its decision would cover the yawning gap left by Aetna and the state Blue Cross plan, which left the market for next year, raising the possibility that no carrier would offer coverage to the bulk of the state’s residents.

Centene, another large insurer, announced its plans last week to offer coverage for the first time in Nevada, Missouri and Kansas.

But other insurers have emphasized they remain ambivalent about staying. Health Care Service Corporation, which operates nonprofit Blue Cross plans, said it would file proposals in all five states where it offers coverage, but could still decide to leave. The insurer covers more than one million people in the individual market.