WASHINGTON — More than 6 in 10 Americans would want Congress to restore federal financial assistance for millions buying health care coverage under President Barack Obama’s health care law if the Supreme Court invalidates some of those government subsidies, a poll said today.

The finding by the nonpartisan Kaiser Family Foundation suggests that a complicated political landscape might await Republicans, who want to repeal and replace the law, should the court annul a crucial part of it later this year.

The court will hear arguments in March in a case that will decide whether Obama’s 2010 law allows federal subsidies only in states that have established their own health insurance marketplaces, and not in states whose markets are run by Washington’s HealthCare.gov. The federal government runs the marketplace in 37 states.

The court’s decision is expected in June.

Should the court strike down the subsidies, Obama and Congress would have to decide what to do. Administration officials have sidestepped questions about their next move. Congressional leaders have made no decisions, but groups of top lawmakers in both the House and Senate have started considering options.

People’s views of the federal subsidies could change over time because few in the poll — just 14 percent — said they know a lot or something about the Supreme Court case.

But in the Kaiser survey conducted earlier this month, 64 percent said if the court rules that subsidies should be available only in states running their own markets, Congress should make people in all states eligible for federal aid. Those favoring congressional action included 82 percent of Democrats, 40 percent of Republicans and 63 percent of independents.

In addition, 59 percent of those in states whose markets are federally run said their state should create its own marketplace if the court invalidates subsidies in their state. People holding that view included just over 6 in 10 Democrats and independents and about half of Republicans.

People with unfavorable views of the overall law outnumbered those who like it, 46 percent to 40 percent.

Across the country, 9.5 million people have so far signed up for 2015 coverage under the law.