House Republicans cobbled together 217 “yes” votes Thursday for a health care plan aimed at repealing and replacing the Affordable Care Act, an accomplishment that looked unlikely as recently as 48 hours ago. That’s a victory worth celebrating for a party that has been defined by its inability to rally its ideologically diverse caucus behind much of anything since re-taking control of the House in the 2010 election. House Speaker Paul Ryan, Majority Leader Kevin McCarthy and Majority Whip Steve Scalise deserve real credit, as does President Donald Trump, who actively worked on-the-fence members over the last few days. But Republicans should be wary of enjoying their success too much – the American Health Care Act faces a decidedly uncertain legislative future in the Senate and its political future is even more murky. You might not have been able to tell from the weeks of deal-making and uncertainty but what happened on the House floor Thursday was the easy part. After all, Republicans control 238 seats in the House and only needed 216 to pass this legislation. In a chamber built around the idea of majority rule, the math and political calculation isn’t all that complicated. Give the people who need passes for political or policy reasons passes and lean on everyone else to be a team player. That battle is now won. But the broader war rages on – and the odds aren’t exactly in Republicans’ favor. The immediate challenge is the Senate, where Republicans hold a narrower majority than in the House – they control 52 seats – and where their members tend to be less conservative, on average, than in the House. Several Republican senators have already voiced concerns about the elimination of the pre-existing conditions mandate and the freezing of Medicaid expansion tat were both included in the House bill. The legislation would also strip out most funding in the ACA for addiction treatment, an issue that will be a larger sticking point in the Senate than it was in the House. While it’s not clear what changes Senate Republicans will make to the AHCA that just passed the Senate, what is clear is that changes will be made. So, even if Senate Majority Leader Mitch McConnell is able to muscle through a piece of health care legislation, that bill would not be a replica of the House version – meaning that it would have to go to a conference committee to resolve the differences between the two. (Conference committee members are appointed by their respective leaders in the House and Senate.) If the conference committee can agree on a compromise bill, that would then have to be voted on in the House and Senate – again. And, we’d likely be back to where we spent the last few weeks – Republicans trying to grind out 216 votes to get it passed. That’s the how-the-bill-becomes-a-law challenge that still awaits the health care bill. The political hurdles may be even more daunting. Start here: The ACA is more popular today than it has been in years; an April Kaiser Family Foundation poll showed 48% of people approve of the law while 41% disapprove. That’s a major reversal for a law that spent most of the time since President Barack Obama signed it with a majority of Americans opposed to it. Then consider the fact that one of the most popular provisions in Obamacare – patients cannot be discriminated against for pre-existing conditions – has been stripped out of the House version of the health care bill. If the mandate is dead in the final law – assuming there is a final law – that could cause major problems for Republicans not only in swing seats and states but also within the Republican base. As I noted earlier, the 11 states with the highest percentage of people under 65 years old with pre-existing conditions are all states Trump won in 2016. The House also passed the bill without a score from the Congressional Budget Office, meaning that they neither knew a) how many people it would (and wouldn’t) cover nor b) how much it would cost. While the Senate won’t be able to vote on the measure until it is scored, it’s possible that House members could lose re-election on the basis, solely, of the fact they cast a blind “yes” for legislation about which they knew very little. Some of the future politics is difficult to forecast because the bill’s future is so uncertain. But Democrats are convinced that the GOP has just handed them a massive issue that will be a critical piece of their push to retake the House majority next November. House Republicans deserve credit for finally getting a health care bill through. But their work is far from done. In fact, it’s only just beginning.