By MJ Lee, Tami Luhby, Lauren Fox and Phil Mattingly

CNN

WASHINGTON (CNN) -- The closely guarded Senate health care bill written entirely behind closed doors finally became public Thursday in a do-or-die moment for the Republican Party's winding efforts to repeal Obamacare.

The unveiling of the legislation marks the first time that the majority of the Senate GOP conference gets a comprehensive look at the health care proposal. With Majority Leader Mitch McConnell pressing ahead for a vote next week, senators only a handful of days to decide whether to support or vote against the bill.

President Donald Trump praised the Senate bill during brief remarks Thursday at a White House "Emerging Technology" event.

"It's going to very good," Trump said. "A little negotiation but it's going to be very good."

The bill is very similar to the version of the House bill that passed last month but with some key changes. The text released Thursday showed the Senate legislation would still make major changes to the nation's health care system, repealing Obamacare's individual mandate, drastically cutting back federal support of Medicaid, eliminating Obamacare's taxes on the wealthy, insurers and others. The Senate plan however would keep Obamacare's subsidies to help people pay for individual coverage.

McConnell's decision to keep the details tightly under wraps until Thursday was intentional and aimed at winning over his colleagues out of the public spotlight, but the secretive process has infuriated Democrats -- and aggravated plenty of Republicans, too.

McConnell has very little room for error -- he can only lose two Republican votes and still pass the bill.

The House passed its version of health care reform last month, but while Republicans celebrated that bill with Trump at the White House, the President has since called it "mean."

Can McConnell get the votes?

Much like in the House, where moderate and conservative lawmakers were deeply divided on health care policy leading up to a vote in May, Senate Republicans also have clashing ideological views and priorities.

Some of the key issues that lawmakers are most concerned about include Medicaid reform, regulatory waivers, the state stability fund and tax credits. McConnell has a tough needle to thread: making significant concessions to conservatives risks losing moderate votes, and vice versa.

What will CBO say?

The legislation will also have to undergo parliamentary scrutiny to ensure that it meets the strict requirements on what can or can't be included in a bill under the budget reconciliation process.

One report that will inform Senate Republicans as they decide whether to support the bill will be a score from the Congressional Budget Office, expected to come out in the coming days.

The CBO analysis will shed light on how much money the bill would cost and how many people would be covered. Senate Republicans hope to see better headlines from this CBO report than the one that the House GOP legislation received. CBO said the House bill would result in 23 million fewer people insured in 2026 than under Obamacare.

What's in the bill and differences with the House

While the Senate bill is largely similar to the House passed-bill, there are some key differences.

Medicaid has been one of the central sticking points in the debate. The bill would continue the enhanced Medicaid expansion funding from Obamacare until 2021 and then phase it out over three years. This is a concession to moderates, who weren't pleased that the House version would end the enhanced support for new enrollees in 2020.

However, conservatives also get some of what they want when it comes to overhauling the entire Medicaid program. The Senate bill would keep the House plan to send a fixed amount of money to states each year based on enrollment or as a lump sum block grant. But it would shrink the program even more over time by pegging the annual growth rate of those funds to standard inflation, rather than the more generous medical inflation, starting in 2025. This would likely force states to cut enrollment, benefits or provider payments.

The Senate bill would also largely maintain Obamacare's premium subsidies structure, but tighten the eligibility criteria starting in 2020. Fewer middle class folks would get help because only those earning up to 350% of the poverty level would qualify, rather than the 400% threshold contained in Obamacare. But it would also open up the subsidies to enrollees below the poverty level so those living in states that didn't expand Medicaid could get some assistance.

Senators opted to keep Obamacare's subsidies to prevent the funds from being used for abortions. The House bill called for creating tax credits based largely on age, but adding abortion restrictions to these credits could have run afoul of Senate rules governing the bill. Still, the similarities to Obamacare will likely infuriate conservatives such as Kentucky Senator Rand Paul, who decried the House version as "Obamacare Lite."

Also, as in the House bill, it would defund Planned Parenthood for one year.

The Senate also backs away from some last minute House concessions to conservatives that would have allowed states to opt out of several protections for those with pre-existing conditions, but insurers would not be allowed to charge higher premiums to those with pre-existing conditions.

The bill would also aim to shore up the existing Obamacare market by allocating funds for the cost-sharing subsidies until 2019. This will placate insurers, who were distraught by Trump's refusal to commit to continue making these payments, leading many carriers to hike rates or drop out of the exchanges for 2018.

CNN's Jeremy Diamond contributed to this report.