The Senate is poised to vote on Thursday on two separate plans aimed at addressing a spike in health care costs that are expected for tens of millions of Americans who receive enhanced Affordable Care Act tax credits unless Congress acts. Both plans, one put forward by Democrats and the other championed by Republicans, are almost certain to fail.

Senate Republicans' proposal to replace expiring Obamacare premium subsidies with pre-funded health savings accounts (HSAs) failed as lawmakers face year-end deadline.

Majority Leader John Thune announced that the Senate will vote on a Republican-led measure alongside a Democratic bill to extend expiring tax credits.

A vote on the possible extension of Obamacare subsidies was a key part of the deal to reopen the federal government last month, which ended the longest government shutdown in American history. Senate Democrats proposed a three-year extension last week on the subsidies that are set to expire at the end of the year.

The hearing comes on the heels of the deadly shooting of two National Guard members in Washington, D.C., by alleged shooter Rahmanullah Lakanwa, an Afghan national.