With no Democrat senators signalling support for the tax reform bill and 51 votes needed to pass the measure, every Republican senator’s vote matters.

With the tax vote expected this week, it’s still unclear how many Republican senators support the legislation.

Sen. John McCain, R-Ariz., has not taken an official position on the Senate tax reform bill, Bloomberg reported, and Sen. Jerry Moran, R-Kan., has been ambiguous on his stance of the bill.

“The easiest way to say this is, I am for some tax bill. Can we find taxes to cut that grow the economy?” Moran said at a town hall in Clay Center, Kansas, according to The Topeka Capital-Journal.

Additional senators who have voiced concerns about the tax reform bill include Sens. Bob Corker, R-Tenn.; Jeff Flake, R-Ariz.; James Lankford, R-Okla.; and Susan Collins, R-Maine.

Both Corker and Sen. Ron Johnson, R-Wis., however, voted to advance the Senate tax plan out of committee in the Senate Budget Committee vote Tuesday afternoon.

On Wednesday, Lankford announced his support of the bill in an interview with CBS News.  

Lankford, Corker, and Flake reportedly expressed concerns that the tax plan will add to the country’s deficit if the revenue predicted in the tax plan does not materialize. The Tax Foundation estimates that the Senate tax plan, “when fully implemented, would spur an additional $1.26 trillion in federal revenues from economic growth.” Corker had suggested that the tax legislation have a kind of trigger that would essentially reverse tax cuts if the projected revenues did not occur.

In an interview with Politico Playbook Wednesday, Sen. Marco Rubio, R-Fla., pushed back on the concerns that the tax bill would adversely affect the deficit.

“The argument would be we can cut taxes because it will drive up the deficit and that assumes that somehow we can fix the deficit through higher taxes and we can’t,” Rubio said.

“The only way you are going to deal with the debt is you have to do two things,” the Florida Republican said, adding:

You’ve got to generate economic growth because growth generates revenue, but you also have to bring spending under control, and not discretionary spending, that isn’t the driver of our debt, the driver of our debt is the structure of Social Security and Medicare for future beneficiaries.

And if we did that, in combination with [economic] growth, you can begin to bring the trajectory of debt to a responsible and respectable level. That is the only way forward, so I think tax reform is the economic growth component of it.

Collins expressed concerns Tuesday about the Obamacare repeal mandate being included in the Senate tax plan.

“If it is going to be included, it’s essential that we mitigate the impact on premiums,” Collins told Politico. “That includes passing the Alexander-Murray bill and also a bill that I have with [Florida Democrat Sen.] Bill Nelson that would protect people with pre-existing conditions, and yet lower premiums through the use of high-risk pools.”

During his interview with Politico, Rubio said including the mandate repeal is meant to help working Americans.

“If you look at the people who are being hurt the most by the individual mandate, it is the individual who is working and isn’t rich but makes $50,000 a year,” Rubio said, adding:

At $50,000 a year, if they don’t have health insurance from their employer, they make too much money for the subsidy, but the law requires them to buy it or they get penalized … they are the ones that get hurt and those are the people we want to focus on helping in this particular circumstance.

Sen. Rand Paul, R-Ky., who was thought to be a wild card on the tax reform plan, announced his support Monday in an op-ed.

“One of the main differences between Republicans and Democrats is that Republicans, in general, favor less government and more tax cuts,” wrote Paul in a Fox News column. “That’s why I’m pleased to see us moving forward on a plan for tax cuts, and why I hope to vote to pass such a cut in the coming weeks.”

Another senator who had been on the fence, Sen. Steve Daines, R-Mont., is now speaking more positively of the tax bill.

“There has been some good progress for Main Street businesses in the tax cut bill,” Daines said. “I was able to secure more than $60 billion in tax cuts for Main Street businesses. … I’ve seen enough progress to vote yes to move the debate forward.”

Johnson, who said Monday that the bill does not do enough to protect pass-through businesses, establishments that are “taxed on the business owner’s tax returns through the individual income tax code,” according to the Tax Foundation, has come to “yes,” according to Axios.

President Donald Trump has been outspoken about reforming the tax code in his first year in office and has said he wants to sign a bill by Christmas.

Adam Michel, a tax policy analyst at The Heritage Foundation, says a tax overhaul is needed.

“The tax plans are not perfect, but Congress is working in a $1.5 trillion reconciliation box and every decision they make is a trade-off against some other priority,” Michel said. “Yes, businesses and many people will still face higher tax rates than they should, and further reductions to all tax rates must remain a congressional priority in 2018 and beyond.”