Senate Democrats unanimously refused to support a Medicare-for-all health care bill on Thursday, with five voting "no" and 43 voting "present."

The bill, proposed by Republican Sen. Steve Daines (Mont.), would have extended Medicare to cover all Americans, Business Insider reports. All 52 Senate Republicans voted against the bill, meaning it did not receive a single yes vote.

Why, then, was the bill put up? To see which, if any, Democrats would back single payer given the chance.

"I do not support a single-payer system, but I believe Americans deserve to see us debate different ideas, which is why I am bringing forward this amendment," Daines said in a statement. "It's time for every senator to go on the record on whether or not they support a single-payer health care system."

Daines' bill was part of the ongoing floor battle over the Senate's version of the Republican health care reform plan, which was originally intended to repeal and replace Obamacare. After a close vote to proceed to debate on Tuesday, the Senate has voted both against the current version of the Better Care Reconciliation Act, the bill offered by Senate Majority Leader Mitch McConnell (R., Ky.), and against a straight repeal of Obamacare without a replacement.

The single-payer amendment was attacked by Medicare-for-all supporter Sen. Bernie Sanders (I., Vt.) as a "sham" and an "old political trick."

But, according to a statement from Sanders, it seems that he may propose an amendment of his own supporting a single-payer system.

"Once Republicans show us their final bill, Sen. Sanders looks forward to getting a vote on his amendment that makes clear the Senate believes the United States must join every major country and guarantee health care as a right, not a privilege," Sanders' office said in a statement.