WASHINGTON — The Senate is preparing for a critical vote, potentially as soon as Sunday night, on a proposal poised to significantly advance efforts to reopen the government.

This vote serves as a pivotal moment to determine whether sufficient Democratic support can be garnered to join Republicans in resolving the deadlock, despite the lack of an extension for Affordable Care Act subsidies that expire at the year’s end. This issue has been a sticking point during the unprecedented 40-day shutdown.

According to insiders speaking with ABC News’ Jonathan Karl, the proposed legislation would secure funding through January 31 and allocate resources for the remainder of the fiscal year to essential agencies. These include the Department of Agriculture, to ensure SNAP benefits, and the Department of Veterans Affairs.

A senior Democratic senator conveyed to Karl that there should be ample Democratic votes for passage, even though a majority, including key leaders, are expected to oppose it.

Democrats would not receive any immediate concessions on healthcare beyond a pledge for a Senate vote on the extension of ACA subsidies by year-end—essentially the same offer Senate Majority Leader John Thune had made over a month ago, which Democrats previously rejected.

While many Senate Democrats are likely to vote against the bill, sources indicate they recognize that this phase of the battle is concluding. They plan to shift the healthcare debate to the midterms, highlighting Republican inaction as a factor that could cause health insurance premiums to soar for millions of Americans.

At least 60 votes are needed to move the bill forward. In past votes, Sen. Rand Paul was the only Republican to vote against the bill while Democrats Catherine Cortez Masto and John Fetterman, as well as Independent Angus King, voted for it. At least five more Democrats would have to vote in favor of the bill to move it forward.

Passage of the bill would not immediately reopen the government. The House would also have to approve the bill. The House has been out of session since September and Speaker Mike Johnson would need to call his members back to Washington to consider this bill before it could head to President Donald Trump’s desk.

The Senate wants to modify the bill in a number of ways. Should the vote succeed, it would start debate of the funding bill. If Democrats allow debate to begin, there are some key modifications that senators want to make to the bill:
-They want to change it’s expiration date from Nov. 21 to the end of January.
-They want to attach three full-year funding bills to it. The government is usually funded through 12 full-year appropriations bills. The three that senators hope to include are Military Construction and Veterans Affairs, the Legislative Branch, and the Department of Agriculture. If lawmakers fail to fund the government by the new deadline, programs covered by these bills would be fully funded through the end of the fiscal year.
-There could be the inclusion of some sort of language guaranteeing Democrats a vote by a certain date on a bill to address health care. There could also be some sort of language to reverse some of the administration’s reductions in force of government workers that occurred during the shutdown.

Unless there’s total agreement by all senators to quickly adjust the bill, it could take the Senate up to a week to process it.

ABC News’ Jonathan Karl contributed to this report.