Congress and the White House, controlled wholly by one political party, take up major legislation to implement sweeping reforms. One of the most senior members of the Senate is unable to participate in critical votes due to a battle with brain cancer. A special Senate election in what should be a “sure thing” seat for the party in power instead breaks to the opposition. Supporters of the bill, seeing grim polling numbers about the legislation, hold tight to the idea that the law will ultimately become more popular once it is implemented.

Yet the bill, increasingly unpopular as passage nears, heightens the potential political peril for its supporters.

Ross Douthat has called it “one of the strange rhymes that history favors,” and certainly the parallels between the passage of the Affordable Care Act and the push to reform the tax code today are many. They are not identical, of course, but there are more than a few echoes of Obamacare’s march to become law that are evident in the current path taken by tax reform.

But more interesting to assess is not the similarities in what has happened, but what the past can (and can’t) tell us about what the future holds. Are there any lessons from what came after the passage of Obamacare that can tell us what might be in store for Republicans if the tax reform legislation becomes law? If Republicans pass a bill that looks unpopular, and hope (as Democrats did) that voters will come to embrace the law once it is enacted and affecting their lives, how is that likely to play out?

Let’s start with the public opinion environment at passage, which is much more negative for the GOP today than what Democrats faced in 2010. When the Affordable Care Act was signed in 2010, Democrats were in perfectly respectable territory on the “generic ballot,” a question pollsters ask to gauge which candidate voters would prefer to see in control of Congress. It wasn’t until Election Day neared that Republicans began opening up a double-digit lead on this question.

In contrast, Republicans today are in a much more challenging spot already, with numerous metrics suggesting it is Democrats who are more motivated to vote in the midterms, and Republicans already trail by double-digit margins with many months to go.

It is fair to debate how much either bill — Obamacare in 2010, tax reform in 2018 — had or will have an impact on the midterms. Pollster David Winston has long argued that it was not frustration about the new healthcare law that drove Republican victories in 2010, but instead economic worry and voters asking “Where are the jobs?" He is backed up by exit polls showing more than 60 percent of voters saying the economy was their top issue, with only 18 percent of voters in that election saying healthcare drove their vote (and with healthcare voters actually breaking for the Democrats). It is also not hard to find a panoply of reasons why swing voters today would be angry with congressional Republicans and President Trump, far beyond any feelings about the tax bill.

But it was clear back in 2010 that Obamacare would present some political risk for Democrats, at least in the short term. Obamacare itself did not become popular until the middle of 2017, when the risk of repeal was the greatest; for the bulk of 2010 after passage, it was unpopular by double-digit margins. And yet, Democrats were willing to vote for it, believing both that it was good policy and that it would eventually become popular once people experienced it in their own lives.

This was a dangerous gamble, but is not unlike the one being made by Republicans staring down 29 percent support for their own bill; if you think it is good policy, and you think people will come around once their paychecks get a little fatter, you may be willing to take the leap anyhow.

Because in the end, Obamacare is still in place. Democrats lost Congress, lost the White House, and yet, the law has persisted. As a thought experiment, I posed a question on Twitter to the Democrats who follow me: If you could go back in time and not have the ACA pass, but in exchange, your losses in the 2010 midterms would be limited and Trump would not become president, would you take the deal? In this entirely unscientific poll, the 600 or so Democrats who responded were divided on the question. (I was frankly astonished to have crafted a question where only a slim majority of Democrats choose the option where Trump does not become president.)

I have heard echoes of this division on the Right in recent weeks. Pass an unpopular bill and brace for impact? The party is already headed for tough times in the midterms. It is unclear if, or how much passage of this bill will alter that dynamic. Furthermore, there is the hope that once implemented, the bill’s support numbers will rise in a way that Obamacare’s did not.

And there’s the near certainty that, come the next Congress, the hope of advancing any conservative policy ideas at all will be greatly diminished. For Republicans in Congress, without a big change in the political environment, it’s now or never.