In reporting on premium increases by one Iowa insurer, the Des Moines Register noted that individuals who bought new plans that complied with Affordable Care Act regulations could face premium increases of 38% to 43% next year. “Another 90,000 Wellmark customers who hold older individual insurance plans are expected to face smaller increases, which will be announced in June,” the paper said.

The disparity stems from a policy proposal in late 2013, when Healthcare.gov was not functioning, millions had received insurance cancellation notices, and President Barack Obama was being heavily criticized for pledging, “If you like your health-care plan you can keep it.” The administration allowed states to extend existing plans for one year.

Some states chose not to take this option. Those that implemented it did so for varying lengths of time. After extending the policy twice, the administration said this year that these temporary extensions would expire by the end of 2017.

States that implemented extensions created an actuarial problem for their health-care exchanges, the market where individuals not insured through their employer can buy their own plans. Enrollees seeking the enhanced benefits provided by Obamacare-compliant plans were the most likely to use them, while many people with little need for additional benefits preferred the status quo. In Iowa the problem is particularly acute: 90,000 residents have pre-Obamacare coverage, significantly more than the 55,000 who had signed up on the exchange as of February. By keeping these people, who tend to be healthier than those with ACA plans, out of the exchanges, the “fix” created another problem, laying the groundwork for the larger premium increases for next year.

The issue is more pronounced in Iowa, but other states are affected. This isn’t the only component of Obamacare that could exacerbate premium spikes. One popular feature is that parents can cover their children up to age 26. At the same time, however, this policy point discourages those young people from buying a plan of their own. Enrollment among these “young invincibles” remains well below expectations three years into the exchanges. Data from 2014 had suggested that those young people enrolling in plans were incurring high medical costs—which could also contribute to a trend of premium spikes.

For every action, there is an equal and opposite reaction. Political solutions from years past may materialize in the form of rate hikes this fall–and could generate a distinct reaction among voters on Election Day.

This post was originally published at the Wall Street Journal Think Tank blog.