WASHINGTON (Reuters) - U.S. Senate Republicans on Monday gained crucial support for a vote on a budget resolution that is vital to President Donald Trump’s hopes of signing sweeping tax reform legislation into law before January.

Two Republican lawmakers, once seen as potential ‘no’ votes, said they would likely support the measure. A third, Senator Rand Paul, may vote ‘yes’ depending on what the final resolution looks like.

“I am leaning ‘yes’,” Senator Lisa Murkowski of Alaska told reporters as the chamber prepared for what is expected to be a late Thursday vote on the fiscal 2018 spending blueprint.

Senator Susan Collins of Maine announced on Sunday that she will likely vote ‘yes.’

Both the Senate and House of Representatives must agree on a budget resolution to unlock a legislative tool known as reconciliation that Republicans need to move tax legislation through the Senate without support from Democrats.

After failing to overturn Obamacare earlier this year, Republicans must pass legislation to cut taxes for businesses and individuals or face a backlash from their constituents in next year’s congressional midterm election campaign.

Though Murkowski said her final decision would depend on what amendments are added to the budget, her qualified support reduces the possibility of failure.

Murkowski was one of three Republicans who sank the Senate healthcare bill in July.

Paul of Kentucky told reporters there is a possibility he will vote yes. “We’re in discussions on it. We’re trying to get it to a document that we think represents what we stand for,” Paul said.

Without a budget and reconciliation, Republicans would need 60 votes in the Senate, where they hold a 52-48 majority.

Republicans usually can lose no more than two votes. But with Senator Thad Cochran of Mississippi ill, their margin of error for the budget has shrunk to only one “no” vote.

Earlier, the White House released a report saying middle-class Americans would eventually see their incomes rise more than $4,000 from the Trump plan to cut the corporate tax rate to 20 percent from 35 percent.

Democrats have lambasted the Trump tax plan as a giveaway for the wealthy.

Trump fired back in a separate tweet on Monday: “The Democrats only want to increase taxes and obstruct. That’s all they are good at!”