Health insurance companies are laying the groundwork for substantial increases in ObamaCare premiums, opening up a line of attack for Republicans in a presidential election year.

Many insurers have been losing money on the ObamaCare marketplaces, in part because they set their premiums too low when the plans started in 2014. The companies are now expected to seek substantial price increases.

“There are absolutely some carriers that are going to have to come in with some pretty significant price hikes to make up for the underpricing that they did before,” said Sabrina Corlette, a professor at Georgetown University’s Center on Health Insurance Reforms, while noting that the final picture remains unclear.

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