WASHINGTON — Millions are expected to forgo coverage if Congress repeals the unpopular requirement that Americans get health insurance, gambling that they won’t get sick and boosting premiums for others.

The drive by Senate Republicans to undo the coverage requirement under former President Barack Obama’s health care law is a sharp break from the idea that everyone should contribute to health care.

And just as important, it fits neatly with the effort by President Donald Trump’s administration to write new regulations allowing for skimpier plans with limited benefits and lower premiums.

Put the two together and the marketplace for about 18 million people buying their own health insurance could look very different in a few years. Consumers would have new options with different pluses and minuses. They’d notice a shift away from health plans that cover a broad set of benefits. New winners and losers would emerge.

Defending the GOP’s move, the Senate’s chief tax writer said Wednesday that the “Obamacare” fines on people who go without coverage amount to a tax on working people. “It’s a terribly regressive tax that imposes harsh burdens on low- and middle-income taxpayers,” said Finance Committee Chairman Orrin Hatch, R-Utah.