(Reuters) - U.S. Republicans made progress on Tuesday in addressing the demands of some key senators in the party about their tax legislation, improving the outlook for the bill’s passage. President Donald Trump and Republican leaders in Congress want to pass a tax bill by the end of 2017. Republicans control the Senate by a 52-48 margin, leaving little room for defections in the face of Democratic opposition. Here is a list of Republicans whose votes are pivotal to the bill’s fate. Senator Bob Corker said on Tuesday he had the outlines of a deal satisfying his concerns that the tax cuts could add too much to the national debt. As a deficit hawk, Corker’s main concern about the plan has been red ink - the tax bill is expected to add $1.4 trillion to the national debt over 10 years. Republicans say that gap would be narrowed by additional economic growth. Under the deal that Corker said he had reached with Senate leaders, the bill would be modified to automatically raise tax revenues if growth targets were not reached. The Tennessee lawmaker, a Trump critic who is not running for re-election, voted to advance the tax plan on Tuesday in the Budget Committee. He also spoke to Trump at a Republican lunch. The two feuded recently, with Corker calling the White House an “adult day care center” after Trump attacked Corker repeatedly on Twitter. The moderate senator from Maine has said she has qualms about Senate leaders’ plan to include repeal of the Obamacare individual mandate in the tax bill. The mandate requires people to buy health insurance or face a penalty. But Trump appears to be making a clear bid for Collins’ vote. Republican Senator Lindsey Graham said on Tuesday that Trump backed a Collins proposal to set aside money to help health insurers cover the most expensive patients. Graham said that provision would probably go into an upcoming government funding bill, along with another measure Collins favors to continue Obamacare subsidy payments for low-income people for two years. Collins told reporters she would offer an amendment to the tax bill to include a deduction of up to $10,000 in property taxes. Collins was among three Republicans who voted in July to block a Republican attempt to dismantle Obamacare, Democratic former Democratic President Barack Obama’s signature healthcare law, formally known as the Affordable Care Act. The senator from Alaska wanted to open the Arctic National Wildlife Refuge, or ANWR, to oil and gas drilling. Provisions to do that were attached to the tax bill as it passed the Budget Committee. Murkowski told reporters on Tuesday she was “feeling better” about the tax bill. She voted against three attempts to dismantle Obamacare earlier this year. But a week ago, she wrote an opinion piece saying she supported repealing the Obamacare individual mandate. Murkowski also wrote that she supported legislation to continue Obamacare subsidy payments for low-income people. Senator Ron Johnson also voted to advance the tax bill in the Budget Committee on Tuesday, although he has been demanding more favorable treatment for “pass-through” businesses as a condition of support. The Wisconsin lawmaker surprised colleagues earlier this month by becoming the first Republican to announce opposition to the tax plan. That earned him a call from Trump. Johnson, formerly chief executive of a polyester and plastics manufacturer, says the legislation unfairly helps corporations over small enterprises organized as non-corporate “pass-throughs.” Those include partnerships and sole proprietorships and account for most U.S. business.   The senator from Montana said in a statement on Monday he opposed the current version of the tax bill because it helped corporations more than other kinds of businesses. “I want to see changes to the tax cut bill that ensure Main Street businesses are not put at a competitive disadvantage against large corporations,” he said. “Before I can support this bill, this improvement needs to be made.” The Arizona maverick and former presidential nominee said on Monday he was still undecided and concerned about “a lot of things” in the tax plan, according to the Wall Street Journal. The war hero infuriated Trump when he joined Collins and Murkowski in voting against the Senate bill last summer to repeal Obamacare. McCain, who is still working after a diagnosis of brain cancer, has said he has almost no working relationship with  Trump. The senator from Arizona, a vocal Trump critic who is not seeking re-election in 2018, has issued a statement saying he was worried about the tax bill’s impact on the national debt. Trump has tweeted that he expects Flake to be a “no” on the tax bill “because his political career anyway is ‘toast.’” Like Corker, Oklahoma conservative Lankford questions whether tax revenues from economic growth will compensate for the expected increase in the national debt under the tax plan.  He has been working with Corker to “trigger” more revenues if needed. “We’re still trying to lock in exactly how we would do it,” he told reporters on Tuesday. The Kansas lawmaker is also wary of the impact on the national debt, pointing to his own state’s recent experience of fiscal problems following tax cuts. A spokesman for Moran said the senator was “determined to pass tax reform” and was working with colleagues to do so. 
Factbox: Republican senators to watch in tax bill fight