There are two central problems facing Senate Republican leaders this week as they try to rush through a health-care bill that's gaining opposition by the day:

1. It's gaining opposition by the day. As of Sunday evening, we count 10 senators who either have strong concerns or who can't support the legislation as is. Republican leaders can afford only two defections of their 52-strong caucus.

2. Not all of their concerns are the same. This bill — the one with 10 senators who could vote against it — is as close as Senate Republican leaders can get to compromise. Any changes to the bill in one direction, say to lessen the impact of Medicaid cuts, will almost certainly make it unpalatable for the opposite side of Republicans' ideological spectrum, such as conservatives who think there's too much government help in health care as is.

Senate Republicans' attempt to roll back Obamacare is a balance between traditional Republican orthodoxy and a recognition that government will probably have a role insuring people for the foreseeable future. On the first point, the bill cuts taxes for the wealthy to grow the economy to give everyone else more money to buy health insurance, if they want it.

But it also keeps some level of government subsidies for people to buy health care, because Republicans don't want to be the party cast as taking away health care people like.

That kind of compromise is necessary to craft a health-insurance bill that won't crater, say health-care experts. Gary Claxton, an analyst at the nonprofit Kaiser Family Foundation, said health-care policy is like a stool. You can't take away the unpopular parts of it, like the tax penalty for people who don't have health insurance, without destabilizing the popular parts, like people having health insurance.

“It's easy to say, 'I want to go down these paths,' " Claxton said, “but once you go down them, they're pretty hard to back their way out of.”

But compromise isn't something Republican senators, both moderates and conservatives, feel like they can sell. Here's what compromise means for Sens. Rand Paul (Ky.), Ted Cruz (Tex.), Mike Lee (Utah) and Ron Johnson (Wis.), who came out against the bill hours after it was introduced: Get rid of most of Obamacare instead of all of it.

“I’ve been telling leadership for months now I’ll vote for a repeal,” Paul said Sunday on ABCs “This Week.” “And it doesn’t have to be a 100 percent repeal.” (The Senate's bill keeps much of Obamacare's structure intact.)

Meanwhile, moderates such as Sens. Dean Heller and Susan Collins feel like they can't go home to people in their states and say: Okay, thousands of you — especially the older, sicker and poorer and people with substance abuse problems — are going to lose health insurance.

“I cannot support a piece of legislation that takes away insurance from tens of millions of Americans and hundreds of thousands of Nevadans,” Heller said in a news conference Friday.

Senate Republican leaders have one key leverage point to try to get three of these five likely “no” votes in line. They can ditch trying to compromise altogether and offer these senators an ultimatum: This is as close as you're going to get to repealing Obamacare. Take it or leave it. And if you leave it, you'll have to explain to your constituents, who have been electing you for years on repealing Obamacare, why Obamacare is still the law of the land.

To that end, a pro-Trump outside group launched a take-no-prisoners ad campaign this weekend accusing Heller of basically standing with Republicans' political enemy, House Minority Leader Nancy Pelosi (D-Calif.).

And President Trump is tweeting this:

So far, though, neither compromise nor ultimatums seem to be working. Opposition to the bill is going up, not down, the more time Senate Republicans have to think about it. Which means it's a very real possibility that, if a vote is held this week, Senate Republicans' health-care bill fails to pass.