Speaker Nancy Pelosi (D-Calif.) is on the verge of pushing ahead with a liberal version of the public insurance option in a health care overhaul, pending the result of a final survey of House Democrats on the issue.

That approach, which would reimburse health care providers at 5 percent over the rates Medicare pays, “is the goal we want to work toward, but that’s contingent on the caucus support,— Assistant to the Speaker Chris Van Hollen (D-Md.) said.

Pelosi asked Majority Whip James Clyburn (D-S.C.) and his team to spend the next 24 hours testing whether the proposal will gather at least 218 votes, top House aides said. Democratic leaders are also awaiting final estimates from the Congressional Budget Office on the preferred version — known as the robust public option — and two others that would rely on rates the federal government would negotiate with providers.

Liberal leaders sounded confident their version would garner the support it needs. “It’s been a lot of toil in the vineyards. But we’re at a point where one final whip, and we’ll see where we’re at, and I think the robust option is going to enjoy the support of 218 plus,— said Rep. Raúl Grijalva (D-Ariz.), co-chair of the Congressional Progressive Caucus. That group’s other co-chair, Rep. Lynn Woolsey (D-Calif.), said a liberal whip count showed their approach gathers more than enough votes if those leaning in support of it are included.

The approach has met stiff opposition from some rural members, who contend it would result in non-sustainably meager payments to hospitals in their districts. But in Pelosi, the liberal version has the most powerful champion it could hope for in the House. She once again made the case for it to her colleagues on Tuesday night, arguing preliminary scores from the CBO show it would garner the most savings and would strengthen the House negotiating position in conference talks with the Senate, one senior staffer in attendance said.

Steven T. Dennis contributed to this report.