By: Niv Elis, The Hill

The Democratic wins in Georgia have elevated Sen. Bernie Sanders (I-Vt.) to a key legislative role in the new Congress.

President-elect Joe Biden’s former primary rival is now set to become chairman of the Senate Budget Committee, where he will wield influence over some of the biggest legislative priorities under the Democratic majority.

The panel sets the terms for budget reconciliation, a procedure that allows senators to approve certain tax and spending bills with a simple majority and sidestep the 60-vote threshold needed for most legislation

With a 50-50 split that will often require tie-breaking votes cast by Vice President-elect Kamala Harris, Democrats are likely to find themselves relying on reconciliation to advance the parts of their legislative agenda most likely to draw full GOP opposition, from more COVID-19 relief, including another round of stimulus checks, to infrastructure, health and climate legislation.

As Budget chair, Sanders will have the opportunity to shape each reconciliation bill, a role fellow progressives are relishing.

“Everybody on the Democratic side wins if we pass the most maximalist proposals that all 50 Democrats can agree on. What Bernie Sanders being Budget chair means is that there will be at least one strong advocate in the room for the maximalist equation,” said Adam Green, co-founder of the Progressive Change Campaign Committee.

The liberal group is advocating for a combined $5 trillion-worth of spending in coronavirus relief and infrastructure spending, based on existing proposals. That amount, Green argued, would be much smaller if the decision making was left to lawmakers like Senate Democratic Leader Charles Schumer (N.Y.) and moderates like Sen. Joe Manchin (D-W.Va.) and Sen. Chris Coons (D-Del.).

“You could see a scenario where it was Schumer, Manchin and Coons in the room, where they’d find things to agree on, but it would be $2 trillion less than what they could have passed,” Green said.

But some argue that the particulars of the budget reconciliation process, combined with a razor-thin Democratic majority in both chambers, could lead to a scenario where Sanders and his committee gavel aren’t as powerful.

“There are things you can do through reconciliation that you couldn’t do otherwise, but if you don’t have a majority that already agrees on the policy, the rules won’t save you,” said Molly Reynolds, a budget expert at the Brookings Institution.

“The fact that the majority is so slim really does mean that Democrats are going to have to get all their members on board.”

While Sanders will be in the room and oversee the process in the Senate Budget Committee, the 50-50 split means just one Democratic senator could sink a reconciliation bill, essentially giving everyone in the caucus the power to torpedo major legislation.

Brian Gardner, chief Washington policy strategist at the investment bank Stifel Financial Corp., said that dynamic means Biden is unlikely to get the full extent of his proposed corporate tax increases, which would deal a major blow to Sanders.

“In order to keep all Democrats on board, including the moderates and lawmakers representing red and purple areas, a tax bill will probably have to be scaled back from what the Biden campaign proposed and what progressives want,” he said.

In some ways, Sanders has already helped push Biden to the left. Biden has dismissed GOP arguments about rising deficits at a time of economic emergency, earning praise from Sanders.

“The president-elect is exactly right that this is not the time for austerity politics,” Sanders told NBC News on Sunday.

But The slim margin could mean the process for a budget bill skips Sanders altogether.

In 2001, the GOP-controlled Congress had an even split in both the Senate and its Budget Committee, preventing it from passing the necessary resolution in committee. Instead, the House did the heavy lifting and sent the final product for an up-or-down vote in the full Senate, a strategy Speaker Nancy Pelosi (D-Calif.) and Democrats may have to mimic.

“If I was advising Mrs. Pelosi and her staff, I’d say your game plan is pretty well laid out from what happened in 2001,” said Bill Hoagland, senior vice president at the Bipartisan Policy Center and a former GOP staff director for the Senate Budget Committee.

A Budget committee split evenly between Democrats and Republicans is unlikely to advance a budget resolution.

“You can just imagine what it would be like with a Bernie Sanders and a Lindsey Graham,” the South Carolina Republican who will serve as ranking member on the panel, Hoagland added.

The House, too, will have to deal with tensions between a progressive wing pushing for bigger, bolder action, and a moderate wing that wants to ensure the deficit doesn’t get out of control.

“We perfectly understand that we are in a COVID-19 emergency, and we understand that climate change itself presents its own emergency, and those are unusual crises that demand a different response on the fiscal side than in many other issues,” said Rep. Ed Case (D-Hawaii), a leader of the centrist Blue Dog Democrats.

“Certainly, we are going to take a very, very close look at any proposal that is developing in the House, that has fiscal implications and ask ourselves the question of whether this in any way, shape or form warrants the same treatment that we did with COVID-19, which was essentially wave PAYGO,” he added, referring to the deficit-control pay-as-you-go rule.

House Budget Committee Chair John Yarmuth (D-Ky.) said “all options are on the table” for Democrats to advance key legislation.

“That includes potentially using reconciliation to advance critical priorities for American families,” he added.

Divisions prevented Yarmuth from advancing a budget resolution last year amid Democratic infighting, but Democrats will have two shots to pass reconciliation bills this year.

“That’s consequential in part because they might try to make choices about what to prioritize in the different bills,” Reynolds noted.

There are thornier questions as to what kinds of policy can actually make it through the labyrinthine rules that govern the budget process.

Reconciliation was originally intended as a tool to let Congress adjust mandatory spending and taxation in order to hit its budget goals.

The rules allow every individual section of reconciliation legislation to be challenged individually.

Any one part can be excluded if the Senate parliamentarian determines that it does not adhere to the requirements. For example, reconciliation bills cannot touch Social Security, nor can they approve discretionary spending. Instead, they must have a clear budgetary effect, and policies cannot be deemed to be “merely incidental” to that effect.

“It’s difficult to say exactly what they can and can’t do, because any individual provision has to be approved by the parliamentarian,” said Reynolds.

While it should be possible to pass stimulus checks, change tax rates and fund emergency vaccine spending through reconciliation, it becomes far more complicated when dealing with infrastructure, climate or even long-held Democratic goals such as raising the minimum wage.

That means that Democrats, and Sanders, may have to think of clever ways to advance their policy goals, without a clear indication of whether or not they will hold up.

“It’s a very complicated process, it’s like a chess game, there are many moves here,” said Hoagland.