Joe Manchin isnt the only person in the Senate with power over Joe Biden s legislative agenda.

The fate of key provisions included in the Build Back Better bill also rests with the Senate parliamentarian the official in charge of advising senators on rules and procedure.

This week, lawmakers and committee staff are meeting with the parliamentarian behind closed doors, in order to ensure the legislation complies with obscure rules governing the budget reconciliation process that Democrats are relying on to pass the bill with a simple majority of votes. The so-called Byrd bath is named after former West Virginia Sen. Robert Byrd, Manchins predecessor, who authored the bill that established the reconciliation process in the first place.

Staff for lawmakers of both parties are expected to present arguments to the parliamentarian, who will then make an advisory ruling as to whether a certain policy can or cannot be included in the bill. The rules allow only for policies that affect the federal budget, such as taxing and spending.

The current parliamentarian, Elizabeth MacDonough, has held the job since 2012. She was recently diagnosed with breast cancer and is undergoing treatment, which could prolong the process.

Its going to move along as fast as she is able, because its just a process that you have to do, Sen. Debbie Stabenow (D-Mich.) told reporters on Monday. You have to meet with the Democrats, meet with the Republicans, meet together, so its just a process.

Asked how many issues are left for the parliamentarian to review, Stabenow said there are a lot.

The parliamentarian operates mysteriously. Generally, they do not issue statements to the public explaining their reasoning. Their office provides summaries of their decisions to senators that sometimes leak to the press.

MacDonough already ruled against Democrats on including a provision in the bill that would have given undocumented immigrants a path to citizenship a setback for advocates working on behalf of the countrys nearly 11 million undocumented immigrants.

Changing the law to clear the way to [legal permanent resident] status is tremendous and enduring policy change that dwarfs its budgetary impact, MacDonough said in a memo to lawmakers in September.

Democrats are now trying to convince the parliamentarian to OK a more narrow proposal giving some undocumented immigrants temporary protection from deportation for a period of five years. Getting some kind of immigration reform measure in the bill is critical to winning support from House progressives, who would get another vote after Senate passage.

Another major Democratic priority included in the bill, a $35 cap on the price of insulin, could also face elimination after possible GOP challenges.

There are different ways, the parliamentarian and other ways the Republicans could try to knock it out, Senate Majority Leader Chuck Schumer (D-N.Y.) said earlier this month.

Republicans are also expected to object to some climate portions of the bill, including those that give tax incentives for the purchase of electric vehicles.

Democrats are hoping to pass the bill before Christmas, but that timeline could slip depending on any parliamentary hijinks, as well as other pressing business on the Senates plate, including funding the government and raising the debt limit.

We continue to meet with the parliamentarian, Schumer said in a floor speech on Monday. Once that is complete, it will be time to bring BBB to the floor.

Manchin, meanwhile, has given no indication that hes on board with Schumers timeline of bill passage by the end of the year. The West Virginia senator has repeatedly urged his fellow Democrats to take a strategic pause, citing rising inflation. This week he added another reason to hit the brakes: concern over the new omicron variant of the coronavirus.

All these things give you cause to pause, Manchin told reporters on Monday.

But Sen. Dick Durbin (D-Ill.), the majority whip, says its time to close the deal on Bidens $1.75 trillion spending plan, which would reduce the cost of child care, offer universal prekindergarten and lower the cost of prescription drugs.

We need Joe Manchins vote to pass it, Durbin said Tuesday during an interview with CNN. I said to him at least a month ago, Joe, you have made your mark on this bill. Youve dramatically cut its cost. You also make sure we pay for anything we do, so it doesnt add to the deficit and its not inflationary. Youve done these things. Now close the deal.