We’ve seen this movie before. Republicans, after a secretive drafting process, finally unveil a health care bill. But the initial reaction is tepid, with both moderate and conservative Republicans expressing “concerns” and demanding changes to the bill.

That’s what happened when the House Republican leadership released its health care bill, the American Health Care Act, in March. And that’s what happened on Thursday, when Republican Majority Leader Mitch McConnell released the Senate’s version of a health care bill, called the Better Care Reconciliation Act.

Soon after the BCRA was officially released, four conservative senators — Rand Paul, Ted Cruz, Mike Lee and Ron Johnson — issued a statement saying that they were “not ready to vote for this bill,” although they also said they were “open to negotiation” about it. This was hardly the only opposition to the bill, however. According to The Washington Post’s whip count, five other relatively moderate Republicans — Susan Collins, Lisa Murkowski, Dean Heller, Rob Portman and Shelley Moore Capito — said they had serious concerns with the bill, ranging from its defunding of Planned Parenthood to its cutting of funds for Medicaid.1 That would seem to put McConnell in a difficult spot: Assuming no Democrats vote for the bill, McConnell can afford to lose only two of his senators.2 But he already has nine senators objecting to the bill from various directions.

We also remember how that other movie ended, however. After a false start in March, when House Speaker Paul Ryan pulled the AHCA from the House floor, Republicans regathered to pass their bill in May by a 217-213 majority.

It’s tempting, therefore, to assume that the same process will play out in the Senate and that the BCRA will eventually pass after a few weeks of drama. When the ink is still drying on the bill, as it is right now, Republican senators have lots of incentive to express their concerns, whether to stake out a negotiating position or to posture before their constituents. McConnell is a skilled vote-whipper, however, and the Senate has generally toed the party line in support of the GOP agenda and President Trump. And even if the bill isn’t exactly the one that senators might want, it’s still in line with longstanding GOP policy objectives.

So all of this probably ends with a big signing ceremony in the Rose Garden — and millions of people losing their insurance, right?

Well, maybe. Betting markets give roughly even odds that key provisions of Obamacare, such as its employer mandate, will be repealed before the end of the year. I don’t know what probability I’d assign to the bill’s passage myself. But I do think it’s worth pausing to take an inventory of some of the differences between the House’s situation and the one the Senate now faces. There are quite a few of these — some of which make the bill more likely to pass and others less so:

  • Republicans need a higher percentage of their members to vote for the bill in the Senate. In the House, the GOP needed 216 of its 237 members3 to support the bill, or 91 percent. In the Senate, they need 50 of 52 members, or 96 percent. This is a big difference. If McConnell can’t nail down the most critical votes — such as Collins, Heller, Murkowski and Paul — he doesn’t have a lot of backup options. This factor is harmful to the bill’s chances of passage.
  • Senators face less immediate electoral pressure than members of the House did. Whereas every member of the House will face voters next year, only eight Republican senators are up for reelection in 2018. And of these, only Nevada’s Heller, Arizona’s Jeff Flake and mayyyyybe Texas’s Cruz look as though they’ll face any real pressure in their general elections. It’s true that the AHCA/BCRA would have profound repercussions for people’s insurance for many years, so the Republicans up in 2020 and 2022 will eventually have to deal with the public fallout if the bill become law. Still, this factor is helpful to the bill’s chances for now.
  • The House had to start from scratch, whereas the Senate can piggyback on the House’s bill. This factor is helpful to the bill’s chances in various ways. McConnell can tell his members that the sky didn’t fall after House Republicans passed their bill. He can tell Cruz and Lee that if the bill was good enough for the House Freedom Caucus, it should be good enough for them. And he can argue that abandoning the bill now — after the House has already taken a tough vote on it — would leave the GOP in the worst of all possible worlds, with swing voters angry at the GOP for passing the AHCA in the House, and base voters angry at them for not getting health care over the finish line in the Senate.
  • Senate Republicans won’t get a “do-over.” One conceit about the House bill, which Ryan may have used to gain leverage with moderate members, was that it would be completely rewritten in the Senate. Just vote on something to keep the process moving, Ryan could argue, and we’ll fix the problems later. But, in fact, the Senate bill turned out to be extremely similar to the House bill. Furthermore, Senate Republicans won’t get a second chance to fix problems with their bill because the House is expected to approve the Senate bill’s “as is” if the Senate passes it, which would send BCRA right to the president’s desk. This raises the stakes and is harmful to the bill’s chances.
  • The Senate must use reconciliation (or Republicans will have to rewrite the rules). Republicans are hoping to use reconciliation to pass the BCRA, which would allow them to pass it with a simple 51-vote majority and avoid a Democratic filibuster. But the Senate parliamentarian has not yet ruled on the bill and will not to do so until a Congressional Budget Office score is released next week. If some parts of the bill don’t pass muster, Republicans will either have to rewrite the BCRA or adopt novel interpretations of the reconciliation rules. (Or if they so choose, they could eliminate the legislative filibuster altogether.) The more drastic the procedural step, the more likely that moderates such as Collins and perhaps traditionalists such as John McCain will object to it. This limits McConnell’s flexibility and is harmful to the bill’s chances of passage.
  • The Obamacare exchanges are in more trouble than they were a few months ago. Obamacare isn’t in a “death spiral” — but it is in a more precarious position than it was a few months ago, with insurers pulling out of markets or substantially raising premiums on a state-by-state basis. (In part, this is because of problems the GOP itself has helped to create.) Trump has claimed that this will create political problems for Democrats and force them to the negotiating table. Polls suggest that Trump is wrong about this: Instead, a Kaiser Family Foundation poll in April found that by a 2-1 margin, voters would blame Trump and Republicans for problems with Obamacare going forward. Nevertheless, this gives McConnell and Trump a certain sort of leverage over congressional Republicans. If Republicans will be blamed either way — for an unpopular bill or for the collapse of Obamacare — there’s no politically easy way out and the GOP might as well pass its bill, McConnell and Trump can say. Therefore, this dynamic is helpful to the bill’s chances of passage.
  • Trump and the bill have grown even more unpopular. Trump’s approval rating was 44 percent when the House first considered the bill in March and about 42 percent when it passed the bill in May. Today, Trump’s numbers are closer to 38 or 39 percent. But the really shocking numbers are on the bill itself. For instance, voters disapproved of the Republican bill by a 59-31 margin in the most recent CBS News poll. (Although the numbers vary some from survey to survey because of question wording, the CBS results are fairly typical of the consensus.) Furthermore, the bill’s numbers are getting even worse as the Republicans’ secretive drafting process hasn’t helped to sell the bill to the public. It’s unusual to see major bills that are this unpopular become law.4 Maybe Republicans will keep the blinders on, but this factor is harmful to the bill’s chances of passage.
  • There have been several special elections since the House vote. Special elections for vacant House seats were held in Montana last month and in Georgia and South Carolina this week. Republicans won all three. At FiveThirtyEight, we look at the margins in these races and not just the winners, which leads us to conclude that these were a pretty bad set of results for Republicans, who won by much smaller margins than the GOP typically does in these districts. But we don’t expect Republicans to see things that way. Instead, we expect these results to give Republicans a morale boost and to be helpful to McConnell’s chances of passing a bill.
  • The news cycle is slowing down, and health care is the lead story again. Paul, Collins and the other Republican objectors won’t kill the bill outright; most have explicitly said they’re open to negotiations. Those negotiations will take time, however. Meanwhile, we’re entering a moment when the political news cycle is seemingly5 slowing down, with no more special elections in the immediate future and the Russia story having been in something of a lull for the past week or two. There’s a reason that McConnell drafted his bill in secret: With a bill so unpopular, he doesn’t want his members to be exposed to public scrutiny about it. But now that voters and the media have fewer distractions, some of his senators will get an earful. This factor is harmful to the bill’s chances of passage.

Finally, there’s the wild card of Trump, who reportedly called the House bill “mean” but praised the very similar Senate bill on Thursday. I’m not going to score that in either direction.

So to tally things up, that’s four “helpfuls” and five “harmfuls.” Furthermore, the first “harmful” — that McConnell can afford far fewer defections than Ryan had — is especially important. Overall, the Senate bill faces a somewhat different and probably also more difficult set of obstacles than the House one did. Therefore, I’d guard both against interpretation that the bill will necessarily pass the Senate because it passed the House. At the same time, Ryan and House Republicans overcame some of the same obstacles — and if that precedent isn’t dispositive, it’s at least highly relevant. Among other things, we know that early whip counts aren’t all that reliable and major legislation often follows a bust-and-boom cycle in which it seems to be falling apart only to come together in the end. Neither Democrats nor Republicans ought to be taking much for granted.