WASHINGTON — Senate Minority Leader Charles E. Schumer Friday worked feverishly to derail Republican momentum toward passage of the GOP's long-awaited tax bill, but it appeared to be a losing effort as Senate Majority Leader Mitch McConnell, R-Ky., confidently predicted: "We have the votes.’’

As the hours and minutes ticked down to a possible vote late Friday or early Saturday, Schumer, D-N.Y., appeared to cede victory to Republicans while shifting his focus to possible blowback.

"Today may be the first day of a new Republican Party — one that raises taxes on the middle class,’’ Schumer said on the Senate floor. "The Republican Party is abandoning its long held principles to please its political paymasters. That is a bad move for Republicans, as well as a bad move for America.’’

Sen. Bob Corker, Tenn., appeared to be the lone Republican "no’’ vote, giving Republicans who control the Senate 52-48 a comfortable margin for passage.

A vote could come late Friday or early Saturday, or it could be delayed once again as it was late Thursday.

Schumer’s press office seized on a non-partisan congressional Joint Committee on Taxation report that punctured the Republican mantra that tax cuts would not blow a hole in the deficit, paying for themselves through expanded economic growth and greater tax revenues.

The report concluded that notwithstanding such growth, the Senate bill would add $1 trillion to the deficit.

The Schumer release cited nearly three dozen quotes from GOP congressional leaders during the Obama era that condemned deficit spending, including one from McConnell calling the deficit and the debt "the transcendent issue of our era.’’

"Until we fix that problem, we can’t fix America,’’ McConnell said in 2013.

Other New York opponents offered up last-minute appeals on what the consequences would be for the state.

Comptroller Thomas DiNapoli questioned whether Republicans fully understood the impact of the tax bill.

"Both houses of Congress are fighting to enact sweeping tax changes that would eliminate important deductions for millions of New Yorkers and threaten higher costs for essential public infrastructure projects,’’ he said in a statement. "Frantically trying to push a flawed piece of legislation over the finish line is not a legislative victory for taxpayers.”

Similarly, health advocates in New York warned of wide disruption in health-care services for vulnerable populations if the Senate bill is adopted. The Senate bill ends the Obamacare "individual mandate,’’ which requires all to have health insurance or pay a tax penalty.

“Eliminating the requirement in current law to purchase health coverage without a replacement leaves cancer patients, survivors and all those with serious illnesses at risk of being priced out of the individual health insurance market,’’ said Julie Hart, New York government relations director of the American Cancer Society Cancer Action Network. "Cancer patients in New York State who need access to affordable coverage could pay more and have fewer choices.’’

The House version of the bill approved Nov. 16 does not address the Obamacare mandate.

If it passes the Senate, the bill would be the most far-reaching tax measure to win congressional approval in three decades.

The Senate bill initially included total elimination of the state-and-local tax (SALT) deduction, a key calculation for those in high-cost, high-tax states like New York.

But one of the last GOP holdouts, Sen. Susan Collins of Maine, tweeted on Friday she was "delighted’’ that her proposal to allow up to $10,000 in property-tax deductions would be in the Senate bill.

The House has a $10,000 property-tax deduction in its bill. Neither Senate nor House bills would continue current-law deductions for state income-tax payments.

President Trump and GOP congressional leaders long promoted the bill as badly needed tax relief for the middle class. But a Congressional Budget Office analysis earlier this week concluded that since the corporate tax cuts are permanent and the personal tax cuts expire after 2025, those earning above $75,000 annually will owe less in tax in 2027 while those earning less will pay more.

The Senate bill lowers the top tax bracket from 39.6 percent to 38.5 percent, doubles the estate-tax threshold to $11.2 million and, similar to the House bill, reduces the corporate rate from 35 percent to 20 percent.

But unlike the House bill, it does not cap new mortgage-interest loans at $500,000, or end itemized medical deductions or phase out the estate tax altogether. In fact, unless Congress agrees to maintain the higher estate-tax level, it reverts back after 2025 to its current level of $5.6 million.

Neither Senate nor House bills touch carried interest, the management fees collected by private equity executives and others in the financial-services industry that are taxed at the lower capital-gains rate instead of the higher one for regular income. Trump himself had expressed approval of the change, but it never materialized in the pro-business GOP tax measures.

Both bills seek to lower rates on "pass-through’’ income that small-business owners pay on their personal income-tax forms. Rates would be as low as 25 percent in the House bill and 31.8 percent in the Senate bill.

But many small-business owners already are paying taxes at comparable rates, and questions arose among some Republicans on whether small-business taxes really would be cut.

Two Republican senators, Ron Johnson of Wisconsin and Steve Daines of Montana, had threatened to vote against the bill because of the "pass-through’’ language. But both ultimately expressed willingness to vote in favor of it, with Johnson saying he’d gotten assurances he would "be at the table’’ when House and Senate negotiators hash out the final language.

Schumer derided the pass-through fix as a sop to wealthier business owners.

"Hedge funds, big fancy law firms, lobbyist firms, would all get a lower rate than the average American because of the pass-through,’’ Schumer said. "The average American who makes $100,000, $200,000 is already paying in the 30- percent range.’’

The Senate bill also fulfills a cherished dream of Republicans: Ending the Obamacare "individual mandate’’ requiring all to have health insurance or pay a tax penalty. But the non-partisan Congressional Budget Estimate reported that while elimination of the mandate would save the government $338 billion, 13 million would no longer have insurance and premiums would rise 10 percent annually for those that do.

dan@hearstdc.com