With negotiations among congressional leaders at an impasse, rank-and-file senators in both parties have for several weeks discussed putting together a proposal that could break the logjam. Several centrist and dealmaker types in the Senate — including Sens. Joe Manchin III (D-W.Va.), Mitt Romney (R-Utah) and Susan Collins (R-Maine) — are expected to push their new bipartisan agreement as a template for legislation that could pass Congress as the economy faces increasing strain from a winter surge in coronavirus cases. The plan set to be released by the bipartisan group seeks to reach a middle ground on numerous contentious economic issues. It would provide $300 a week in federal unemployment benefits — a lower amount than the $600 per week sought by Democrats, while still offering substantial relief to tens of millions of jobless Americans — for four more months. The agreement includes $240 billion in funding for state and local governments, a key Democratic priority opposed by most Republicans, as well as a six-month moratorium on some coronavirus-related lawsuits against firms and other entities — a key Republican priority opposed by most Democrats. Aides close to the effort described details as fluid and subject to change. The effort still faces enormous hurdles, and most congressional aides are skeptical that the push will successfully turn into new legislation. President Trump’s negotiators have remained at odds for months with House Speaker Nancy Pelosi (D-Calif.) over multiple critical aspects of stimulus legislation, while Senate Republicans led by Majority Leader Mitch McConnell (R-Ky.) were broadly uncomfortable with the amount of spending pushed at times by the White House. But the substantive efforts at a compromise in the Senate reflect growing agitation from influential senators against the hard-line stances of their respective leaders, who have struggled to reach another round of coronavirus relief aid even as the economy continues to suffer under the weight of the pandemic. McConnell and Senate Minority Leader Charles E. Schumer (D-N.Y.) have publicly traded barbs, with McConnell on Monday accusing Democrats of “all or nothing obstruction.” Schumer said in a floor speech that “both sides must give” but also trashed McConnell for advancing a GOP wish-list in stimulus talks. Some lawmakers have hoped that elements of a bipartisan stimulus deal could be added to the spending bill required to avoid a Dec. 11 government shutdown, although that could complicate must-pass legislation. Economists have warned of devastating consequences for the economy and millions of Americans if no stimulus deal is passed. A number of relief programs are set to expire at the end of the year; 12 million Americans are on pace to lose their jobless benefits, and protections for renters and student borrowers are also set to expire. But the White House has largely abandoned its aggressive push for stimulus since Trump lost the Nov. 3 presidential election. It is also unclear whether President-elect Joe Biden will push Democrats to accept a smaller package, although some of his economic advisers have been adamant that a stimulus deal must be urgently passed even if it is smaller than what Democrats prefer. Among those involved in the latest effort include Democratic Sens. Manchin, Jeanne Shaheen (N.H.), Maggie Hassan (N.H.) and Mark R. Warner (Va.), as well as Angus King (I-Maine), who caucuses with Democrats. Sen. Richard J. Durbin (D-Ill.), the second-ranking Democrat in the Senate, has also been involved in the discussions but won’t appear at a news conference later Tuesday unveiling the plan. Among the Republicans involved are Sens. Lisa Murkowski (Alaska) and Bill Cassidy (La.), in addition to Romney and Collins. The bipartisan agreement includes about $300 billion in funding for small businesses through the Paycheck Protection Program, aides said. It also includes $40 billion to assist hard-hit transit agencies and rental assistance funding for those facing eviction, as well as about $50 billion in health care, including to help with vaccine distribution and testing and tracing of the coronavirus. The effort was expected to leave out a second round of $1,200 stimulus payments, as a way to bring down its overall price tag, even though that measure is supported by both Trump and Pelosi.