It took a lot to get to this point, but Republicans have released their long-awaited health care bill. (For more on the policy, check out the NPR health team's reporting over at Shots.)

The version that was released is likely to change as the bill goes through committees, but now that it's released, here are four potential challenges President Trump and Republicans face:

1. Health care is complicated

"It's an unbelievably complex subject. Nobody knew that health care could be so complicated."

That's what President Trump told a gathering of governors about the health care system last week. President Obama was his team's best messenger on health care — and the message still got very muddled. Republicans were effectively able to drum up fear and opposition because when something is so "unbelievably complex" and "so complicated," it's easy to pull out portions that can be spun as offensive.

What's more, Obama deeply understood this policy. Remember, most of the 2008 Democratic primary debates revolved around health care and mandates (which became Obama's greatest flip flop). Does Trump really understand what's being sold or does he just want to declare victory and put his name on it? So who is the messenger going to be — and who's going to arm members with the clarity and talking points they need?

Trump has been a very effective messenger when it comes to being against the Affordable Care Act, also known as Obamacare. That's the easy part.

The challenge now is trying to sell something he wants people to be for.

And there's always this complication — Trump might be currently touting the plan, but what happens if things go south? Does it suddenly become Ryancare?

2. Rebellion from within — right and center

Because Republicans don't need 60 votes to overcome a filibuster, their biggest hurdle is themselves. In 2009, remember progressives clamored for a "public option." That led to the White House spokesman deriding them as the "professional left," a term one might more expect to come from the Trump White House rather than Obama's.

Fast forward to 2017, and just because Trump won, it doesn't mean everyone in the GOP is ready to fall in line. There are lingering feelings among some in the base that not only is Trump not a true fiscal conservative, but neither is House Speaker Paul Ryan or Republican Senate leader Mitch McConnell.

It's the same faction that thwarted the "grand bargain," pushed the government to a partial shutdown over the debt ceiling and eventually ousted a speaker. Don't underestimate this group and their ability to stir rebellion. Get ready to hear much more about their opposition to "refundable tax credits," which many conservatives see as nothing more than a new entitlement, or the $100 billion fund the bill creates.

Michael Needham, CEO of Heritage Action for America, went so far as to say in a statement: "In many ways, the House Republican proposal released last night not only accepts the flawed progressive premises of Obamacare but expands upon them."

That's not to mention provisions that moderates — Maine's Susan Collins and Alaska's Lisa Murkowski — won't like, including changes to Medicaid and efforts to dismantle Planned Parenthood. As NPR's Susan Davis notes, a group of GOP senators from Medicare expansion states sent a letter Monday voicing concerns, and they would be tough votes for Collins and Murkowski if the bill includes Planned Parenthood defund language in the end.

And remember, given that Republicans have only 52 senators, they can afford to lose just two votes (with Vice President Pence again needing to be called in to break a tie).

3. "Resistance" and resentment

While Democrats don't have the votes to stop the bill, that doesn't mean they'll go quietly. There will be zero Democratic support, which makes Ryan's and McConnell's jobs that much tougher, and town halls can cut both ways, as we've already seen. In 2009, the potential bipartisanship around health care was blown up by those town halls.

Former Sen. Olympia Snowe of Maine and Iowa's Chuck Grassley, for example, by the time they got back to Washington after summer recess, they were all but off the train paying not much more than lip service to the potential for voting for it. Remember Snowe's so-called "trigger" option, designed to get that one whiff of bipartisanhip? It never happened. Expect Republicans to get an earful across the country.

4. Cost and perception

Three little letters for you: C, B, and O. The fight in 2009, and the strongest talking point Democrats had, was that the Affordable Care Act would "bend the cost curve." Republicans fumed at the Congressional Budget Office's projection that it would save the government money in the long run. So what about this plan? We don't yet know, because the CBO hasn't scored the bill yet. But early signs aren't promising for Republicans. Full and partial repeal projections showed it potentially blowing a gaping hole in the budget.

It's tough to balance the budget when a lot of the money going in, comes out (the mandate and tax revenue streams).

Republicans, who are supposed to be fiscal conservatives, risk being perceived as the party trying to strip people of their health care, returning the system to the status quo — and blowing a hole in the budget.

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