The White House and House Speaker Paul Ryan must do some serious arm twisting if they are to push the GOP's current plan to repeal and replace Obamacare through the House on Thursday.

President Trump started doing just that on Tuesday when he met with the House Republican Conference to encourage party holdouts to support the package. The president delivered a warning that GOP lawmakers described as good-natured in tone, but taken literally doesn't sound friendly in the least. "I'm gonna come after you, but I know I won't have to, because I know you'll vote 'yes,'" said the president, several Republican lawmakers who attended the closed-door meeting told reporters. "Honestly, a loss is not acceptable, folks."

Trump's aggressive stance is easy to understand: the most conservative Republican lawmakers oppose the plan put together by Republican leaders and the White House, deriding it as "Obamacare-lite."

Monday night House leaders made many small revisions to the bill in order to draw more support, but the indication Tuesday was that the efforts have persuaded few if any conservatives.

Should the legislation ultimately be enacted, the biggest beneficiaries among public companies are likely to be the largest health insurers, including Anthem (ANTM) - Get Report , UnitedHealth (UNH) - Get Report , Cigna (CI) - Get Report and Humana (HUM) - Get Report .

Hospital stocks such as Tenet (THC) - Get Report , HCA (HCA) - Get Report and LifePoint (LPNT) are likely to suffer from cuts to healthcare providers' revenue.

Republicans are also pushing a number of bills unrelated to Obamacare but that are nevertheless part of the GOP's effort to revamp the healthcare system. Also on Tuesday, the House began floor action on a bill establishing rules for association health plans, which would give small employers and other groups the ability to band together and create insurance pools. There is also legislation to restrict lawsuits and damage awards against health providers whose services were subsidized by the federal government.

Two GOP healthcare bill may actually win some Democratic support. One, also debated on the House floor Tuesday, would eliminate health insurers' antitrust exemptions and the other would forestall federal regulation of stop loss coverage for self-insured group health plans.

GOP opposition to the Obamacare repeal bill is organized by the House Freedom Caucus, which controls enough votes to sink the bill. The caucus has 29 members total and the GOP can afford to lose only 21 votes and still achieve the 216 votes need to pass the bill, assuming Democrats remain united against the bill.

House Freedom Caucus Chairman Rep. Mark Meadows, R-N.C., said Tuesday that Trump failed to make the case for dropping the group's opposition. Meadows said he's had no notice from any Freedom Caucus member that intends to support the bill.

"I think it makes it very difficult if not impossible to get to 216," Meadows said.

The deal faces even more serious obstacles in the Senate, where the Republican majority is so slim that the GOP can afford to lose only 2 votes. There, at least three GOP senators have come out opposed to the bill, Rand Paul of Kentucky, Mike Lee of Utah and Ted Cruz of Texas. Although their opposition is in line with that of the House Freedom Caucus, other GOP critics in the Senate contend the bill goes too far to eliminate the government's role in healthcare.

The House legislation repeals many of the taxes and mandates imposed to help pay for Obamacare and would establish tax credits and expanded healthcare savings accounts as the mechanism for replacing ACA subsidies that have made it more affordable for individual consumers to purchase coverage on state health insurance exchanges. The plan also phases out the ACA's expansion of Medicaid, the health insurance program for the poor.

The revisions offered up Monday night allow the Senate to revise the tax credit provisions, presumably by making them more generous, for older, low-income individuals. That provision was aimed a luring more support from GOP moderates in both the House and Senate. For conservatives, the House leadership added a provision that will prevent states that haven't already signed onto Obamacare's Medicaid expansion from doing so now. The Affordable Care Act's taxes would also be repealed more quickly than under the draft passed by the House Budget Committee last week. Also added were new work rules for the Medicaid program and an option for states to receive Medicaid block grants. More restrictions on the use of taxpayer funds for abortions were added. And, in New York state, county governments were allowed to shift Medicaid costs to the state.

But the Freedom Caucus as a whole appears unsatisfied by those changes. Among the changes they continue to seek: a repeal of the ACA's mandated minimum benefits for insurance plans.

Meadows said the Freedom Caucus members are free to vote for the bill if they wish and the caucus will not take an official position. Nevertheless, he said he has not seen any changes sufficient for any of them to drop their opposition.