The ongoing U.S. government shutdown is about to become the nation's longest federal funding lapse ever.

The shutdown is poised to hit that milestone on Wednesday, marking its 36th day and surpassing the previous record, which was set in early 2019.

The latest attempt to break the logjam, by getting a Republican-backed stopgap measure passed by Congress, failed in the Senate for the 14th time on Tuesday.

There are no further votes scheduled Tuesday on the GOP's short-term continuing resolution, or on an alternative proposal put forward by Democrats, which includes additional spending on health care and other priorities.

Both of the longest government shutdowns in U.S. history occurred while President Donald Trump was in office.

The funding dispute centers on enhanced tax credits for insurance premiums under the Affordable Care Act, which are set to expire by year's end, threatening to significantly hike health care costs for millions of Americans.

Democrats have refused to vote for any "clean" stopgap resolution that does not address those subsidies. Republicans have rejected the prospect of negotiating while the government remains shut down. While Republicans hold a narrow majority in the Senate, they need Democratic votes to overcome the chamber's 60-vote threshold.

Some Republicans on Tuesday said they have grown "optimistic" that the shutdown could end this week.

Sen. Mike Rounds, R-S.D., told reporters that he believes Democrats will be more open to cutting a deal after breaking the shutdown length record and after Tuesday's elections are complete.

They will be able to tell their constituents "we're fighting the President, and I think that's a major part of what this is about," Rounds said.

Sen. Markwayne Mullin, R-Okla., said he was "pretty confident" the shutdown would end in the coming days.

But some Democrats have poured cold water on the prospect of a coming compromise.

"There seems to be some indication of a thaw, but I see no immediate solution on the horizon," Sen. Richard Blumenthal, D-Conn., said.

"Talks are a good thing, but so far, I sense no willingness on the part of Republicans to really assure the American people that health care insurance will be guaranteed," he said.

Sen. Elizabeth Warren, D-Mass., asked about Republicans' optimism, said, "That would be nice. I hope that means Republicans are coming to the table to negotiate with Democrats, because so far, they have come to the table to negotiate exactly zero times."

This is developing news. Please check back for updates.