WASHINGTON (AP) — There's growing evidence that most of the nation's dramatic jump in health care coverage is due to President Barack Obama's law, and not the gradual economic recovery.

That's going to raise election-year political risks for Republicans who keep campaigning to repeal "Obamacare" without a plausible substitute.

Why? Consider GOP front-runner Donald Trump's "repeal and replace" plan. A nonpartisan analysis says it would push 20 million people back into the "uninsured" category — a recipe for political backlash.

The share of Americans without health insurance has dropped to about 9 percent, a historic low. But even as the economy expanded, major government surveys show lackluster improvements in job-based coverage.

The health care law is becoming a backstop in a changing economy.