Sen. Steve Daines (R-Mont.) wants Democrats to show their cards on single-payer healthcare.

The GOP senator has filed an amendment to implement a government-funded healthcare system in a political maneuver aimed at forcing Democrats to say whether they support the concept that is picking up steam on the left.

A vote on the amendment has been scheduled for Thursday.

It's almost certain Daines doesn't support a single-payer system.

The vote would be part of the ObamaCare repeal bill vote-a-rama - a rapid succession of amendments that can last hours, oftentimes stretching through the night and into the next early morning. Vote-a-ramas are often a time when senators force their colleagues across the aisle to take tough votes, which can be turned into political attack ads later.

During the 2016 Democratic presidential primary, Sen. Bernie Sanders (I-Vt.) championed the idea of "Medicare for All."

It's gained traction as more Democratic candidates have embraced the idea. Recently, senators such as Elizabeth Warren (D-Mass.) and Kirsten Gillibrand (D-N.Y.) have rallied around universal coverage. And a Medicare-for-all bill in the House has already garnered 115 co-sponsors, which is almost double the amount the legislation received last congressional session.

Senate Democrats have to defend 23 seats next election and another two held by independents who caucus with the Democrats. Those up for re-election include Sens. Jon Tester (D-Mont.), Bill Nelson (D-Fla.), Joe Donnelly (D-Ind.) and Claire McCaskill (D-Mo.).

The legislation from Daines appears to be the same language as the Medicare-for-all bill in the House sponsored by Rep. John Conyers (D-Mich.).

But single-payer isn't a unifying message among Democrats.

"It'll tend to be an issue that more left-leaning Democrats are willing to embrace," said Dan Mendelson, president of consulting firm Avalere Health, told The Hill earlier this month.

"In order to embrace that concept, you'll have to be willing to defend the efficiency and effectiveness of a fully run government system, and there are many Democrats who are not going to do that and there are some who are."

Yet, healthcare has also divided the Republican conference, fractions which one Democrat said could speed up the timeline of a single-payer system becoming a reality.

"They have made the public more aware of Medicaid than ever before, specifically, and healthcare generally," Rep. Earl Blumenauer (D-Ore.) said Wednesday at The Hill's Health Rx: Building Affordability & Access event. "They've accelerated the move toward single-payer, probably advancing it by a decade."

Jordain Carney contributed to this report