The Senate Budget Committee on Tuesday approved the Republican tax bill, a crucial procedural step toward a vote by the full chamber later this week.
With the party-line 12-11 vote to advance the plan, Republicans overcame one possible roadblock in their push to chop tax rates for businesses and individuals by the end of the year.
Two GOP members of the panel had separate concerns that threatened to upend the bill's momentum. Sen. Bob Corker, R-Tenn., wants a "trigger" to raise revenues should the bill's economic growth effects not go far enough to make up for the nearly $1.5 trillion in estimated tax cuts over 10 years. The senator had fears about expanding budget deficits and suggested Monday that he could vote "no" to advance the proposal.
In a statement Tuesday, Corker said he backed the bill after reaching a tentative deal on a "trigger" to "ensure greater fiscal responsibility should economic growth estimates not be realized." The senator added that the proposal needs to be finalized but said he is "encouraged."
Meanwhile, Sen. Ron Johnson, R-Wis., sought to further reduce the tax burden on pass-through businesses, which pay individual rates. He argued that those businesses got worse treatment under the plan than corporations, which would see their tax rate chopped to 20 percent from 35 percent.
Both senators ended up voting to advance the bill. Johnson later said he got assurances that his concerns would be addressed either in the Senate bill or in a joint bill with the House.
Senators going to the hearing were greeted by protesters shouting "Shame!" and "Kill the bill!"
Republican Senate leaders want to pass the plan later this week. As it holds 52 seats, the GOP can lose only two votes and still approve the bill under special budget rules, assuming all Democrats and independents oppose it.
Though the fiscal trigger earned Corker's support, other senators quickly criticized the measure.
"I am not going to vote to implement automatic tax increases on the American people. If I do that, consider me drunk. I'm not voting for that," Sen. John Kennedy, R-La., said, according to Bloomberg.
Sen. John Thune of South Dakota, the third-ranking Senate Republican, said, "It's not in our best interest to have a mechanism that would create a tax increase," Bloomberg reported.
Shortly before the budget committee vote, Senate Majority Leader Mitch McConnell called it a "challenging exercise" to get enough support to pass the bill.
"Think of sitting there with a Rubik's Cube trying to get to 50 [votes]," the Kentucky Republican told reporters. "And we do have a few members who have concerns and we're trying to address them. And we know we will not be able to go forward until we get 50 people satisfied, and that's what we're working on."
The Senate proposal would temporarily cut many individual income taxes while permanently reducing the corporate rate. It would also change or eliminate some popular deductions.
Multiple other senators have expressed similar concerns to those of Corker and Johnson.
Speaking to reporters Tuesday after a meeting with McConnell and House Speaker Paul Ryan, President Donald Trump said, "I think we're going to get it passed." The president added that he expects "lots of adjustments" before a final plan gets approved. He did not specify what those adjustments would be.
At a Senate GOP lunch earlier in the day, Trump "underscored the importance" of passing a tax bill, according to McConnell.
Trump later described the meeting as "phenomenal," "very special" and a "love fest."
— CNBC's Ylan Mui contributed to this article.