President Trump will likely have to issue his first veto to keep in place his national emergency declaration. But based on what we know now, the veto is unlikely to be overturned.

The House voted 245-182 Tuesday to overturn Trump’s declaration, which would free up money to build more physical barriers along the U.S-Mexico border. Thirteen Republicans joined 232 Democrats to vote yes. But that was the easiest part — it gets progressively harder for opponents of Trump’s emergency from here. Next, the resolution goes to the Senate, where it needs only a simple majority to pass. If the resolution passes the Senate, Trump will presumably veto it, in which case a two-thirds majority would be needed in each chamber to override the veto.

The Senate looks likely to pass the resolution, but not by a veto-proof majority. Alaska’s Lisa Murkowski and Maine’s Susan Collins, both of whom break with Trump more than most other Senate Republicans, and North Carolina’s Thom Tillis have already said they will back the resolution. Assuming all 47 Democratic senators vote “yes” (this is a safe assumption, none have signaled they will break ranks), one more Republican defection would allow the provision to pass. And there are more than a dozen Republicans who have raised concerns about Trump’s declaration, with many of them casting it as an overreach of executive power that they worry will set a precedent for the next Democratic president.

In terms of additional Senate defections, I’m looking for four kinds of senators who would be more likely to join with Democrats. First, there are the more moderate Republicans, both of whom are accounted for: Collins and Murkowski are expected to vote for the resolution. (There aren’t many true moderate GOP members left in the Senate.) More moderate Republicans were clearly more likely to break with Trump in the House on Tuesday. The 13 Republicans who voted “yes” with the Democrats had an average Trump Score of 83 percent, well below the average among the “no” votes, 94 percent. (Of course, plenty of Republicans with relatively low Trump Scores, in the mid-to-high 80s, voted “no” also.)

Second, keep an eye on the GOP senators who are the most electorally vulnerable in 2020, running in states that Hillary Clinton either won or narrowly lost. Again, Collins falls in this bucket, but so too does Tillis. Colorado’s Cory Gardner and Arizona’s Martha McSally, who haven’t tipped their hands yet, also qualify. For these senators, showing some independence from Trump might be smart politics. In the House, the average Republican to break with Trump on Tuesday came from a district with a FiveThirtyEight partisan lean of about R+16; the average “no” Republican came from a R+28 district.

Then, there are the statesman senators, such as Tennessee’s Lamar Alexander, Utah’s Mitt Romney, and Nebraska’s Ben Sasse. They like to project images that they are above partisanship and instead act in the national interest. I would not be surprised if one of these men joins the Democrats.

Finally, watch Utah’s Mike Lee and Kentucky’s Rand Paul, who I would categorize as kind of maverick-y in the Senate.

So let’s assume at least one of those Republicans joins Collins, Tillis and Murkowski and this bill passes the Senate, but is then vetoed by Trump. That veto is likely to stand.

Only 13 of the 195 House Republicans who voted on the measure joined with the Democrats, far below the more than 50 House Republicans who would be needed for a veto override. Even if all of the Republicans in the most competitive districts who voted with Trump this time around decide to vote with the House Democrats in the next vote, the resolution would still need more than two dozen additional votes from Republicans to pass the House. Those would have to come from members in clearly conservative districts (those that lean more than 10 points toward the GOP). That is unlikely, particularly since Republican voters overwhelmingly support Trump’s national emergency policy.

In the Senate, 20 Republicans would need to join Democrats to override a Trump veto, but there aren’t nearly that many GOP members who come from purpleish states and break with Trump relatively often. I made a list of every Senate Republican that somewhat resembles the Republicans who voted “yes” in the House and I got only 10 names: Murkowski, Collins, Rick Scott, Mike Braun, John Kennedy, Josh Hawley, Steve Daines, Patrick J. Toomey, Lindsey Graham and Ron Johnson. And it’s hard to imagine even some of those 10 voting to overturn a presidential veto.

In short, on the national emergency policy, Trump’s party is not totally unified behind him, but for now, they appear to be unified enough.

House votes to end Trump’s national emergency