(ABC News)–Two key Republican holdouts have done a 180-degree turn and now support the GOP tax bill: Sen. Marco Rubio, R-Fla. and Sen. Bob Corker, R-Tenn.

While several Republicans say they are still waiting to see the final bill, right now, it does not appear a single Republican is on the record as a “no” vote.

Rubio, who on Thursday was a “no’ vote, now appears on board after Republicans expanded the child tax credit.

Corker, who was the sole Republican to oppose the original Senate bill over concerns about the deficit, is also now a yes.

“After great thought and consideration, I believe that this once-in-a-generation opportunity to make U.S. businesses domestically more productive and internationally more competitive is one we should not miss,” Corker said in a statement.

“In the end, after 11 years in the Senate, I know every bill we consider is imperfect and the question becomes is our country better off with or without this piece of legislation. I think we are better off with it. I realize this is a bet on our country’s enterprising spirit, and that is a bet I am willing to make.” he concludes.

Senator Mike Lee, R-Utah also has serious concerns about the bill for the same reason, his office confirmed on Thursday.

Lee’s office has not responded to ABC News’ request on Friday for an update on his stance.

The potential absence of Senator John McCain, R-Ariz., could complicate the bill’s chances.

McCain, who is undergoing treatment for an aggressive form of brain cancer, was not at work Thursday in the U.S. Senate. His office reported that he is “receiving treatment at Walter Reed Medical Center for normal side effects of his ongoing cancer therapy.”

House Speaker Paul Ryan said that considerations of absences in the Senate could impact which chamber takes the first votes.

“There is discussion about this,” Ryan said. “It’s all about timing and managing absences in the Senate.”

GOP leaders are optimistic that they will get this done.

Asked if he’s confident this will pass, Sen. John Cornyn, R-Texas, responded with just one word: “yes.”

The final conference report with full details is expected to be unveiled by Republican negotiators Friday – teeing the measure up for a vote in both chambers next week.

Here is what ABC News has learned will be included in that bill:

FOR BUSINESSES — Corporate rate will be cut to 21 percent, down from 35 percent under current law. This is expected to take effect in 2018.

— Corporate Alternative Minimum Tax will be “rolled back” according to Sen. John Cornyn – but not repealed.

FOR THE WEALTHY

— Top individual rate will be cut to 37 percent, down from 39.6 percent under current law.

— Individual Alternative Minimum Tax exemption will be increased to $500k for individuals, $1 million for couples filing jointly. That’s up from $54,300 for individuals, and $84,500 for couples filing jointly under 2017 law.

FOR THE MIDDLE CLASS

— Standard deduction will be increased from $12,700 to $24,400 for joint returns and from $6,350 to $12,000 for individuals. According to the Tax Policy Center, more than two-thirds of Americans take the standard deduction when filing taxes.

— Repeal of the individual mandate requiring health insurance. According to CBO, repealing Obamacare’s individual mandate insurance could lead to 13 million more Americans without health insurance, while saving the government $338 billion in federal health insurance subsidy payments over the next decade.

FOR THOSE WHO ITEMIZE

— State and local tax deductions will be capped at $10,000 combined from any/all categories (property/income/sales taxes). Current law caps property tax deduction at $1 million. There are no current caps on state/local income tax deduction.

— Mortgage interest deduction will be capped at $750,000, down from $1 million under current law.

— Graduate school stipend deduction (tax-free tuition waivers) will be preserved.

— Student loan interest deduction will be preserved.

— Medical expense deduction is preserved. It allows Americans to deduct medical expenses not covered by insurance that exceed 10 percent of adjusted gross income.

— Child Tax Credit preserved. That’s currently set at $2,000 per child but only refundable up to $1,100. It remains to be seen whether Rubio’s push to increase that will be reflected in the final bill.

The tax overhaul process has moved at a breakneck pace as Republicans try to pass a massive tax cut for businesses and many American families before Christmas and the end of the year. Many lawmakers and their staffs have been scrambling to digest drafts of the bill and what it means for everyday Americans.

The cost of the measure remains another lingering question. The negotiators still need to work with the Joint Committee on Taxation (JCT) to secure a final score on the bill’s cost.