The most important effects stemming from Justice Anthony Kennedy’s retirement will be on how the Supreme Court rules on landmark cases on issues ranging from abortion to gerrymandering. But there are fewer than 20 weeks between now and the midterm elections, and Kennedy’s announcement also has the potential to affect the composition of the next Congress.

Betting markets see the news as a wash as far as the midterms go. But betting markets are sometimes pretty dumb, so let’s work our way through a pair of decent arguments I’ve seen for why Kennedy’s retirement is more likely to help Republicans than Democrats politically :

Argument No. 1: Kennedy’s retirement will help Republicans close the “enthusiasm gap”

One way that Kennedy’s retirement could help Republicans is by narrowing the enthusiasm gap between Democrats and Republicans. Here’s how National Review’s David French puts it:

Heading into the midterms, Republicans were desperately worried about an “intensity gap.” Democratic voters seem prepared to turn out in huge numbers. Republicans — while holding firm in their support for President Trump — lacked the same excitement. Special elections were swinging strongly Democratic, and even though the generic preference numbers were trending closer, most observers thought Republicans would struggle to get their voters to the polls. I’d say those concerns are eased a bit today. After all, for an immense number of base GOP voters, judges aren’t just an issue. They’re the issue that drives them to the polls. Republicans are all over the place on immigration policy, trade policy, and foreign policy. Divisions in the party are deep and real. Those divisions disappear when judges are on the line. We can debate all we want about Russian influence on the 2016 election (or about the effect of the Comey letter), but one thing is certain — if Evangelicals and other conservatives weren’t afraid of the impact of a progressive Supreme Court on their fundamental liberties, Donald Trump doesn’t win. A new Supreme Court pick will galvanize the entire base for months.

This is a well-argued case. French is certainly right that an enthusiasm or intensity gap is a massive risk for Republicans. If the midterm elections look more like the special elections we’ve had so far this cycle, in which Democratic turnout significantly outpaced Republican turnout, the GOP is very likely to lose the House and the Democratic wave could reach epic proportions. But without that enthusiasm gap, control of the House looks like more of a toss-up, at least based on the current generic ballot average.

Democratic candidates will undoubtedly also try to use the Supreme Court as a wedge issue. If and when Trump’s nominee is confirmed, these candidates will pivot to telling their voters about how a Republican-chosen replacement for Ruth Bader Ginsburg (who is 85 years old) or Stephen Breyer (79) would be an even bigger problem and how it’s therefore crucial that Democrats take control of the Senate.

The catch, though, is that the Democratic base is already very motivated: Motivated by the Russia investigation, by Republican efforts to repeal Obamacare, by Trump’s overall unpopularity, and so forth. They might not need the additional motivation of a Supreme Court nomination, whereas Republican voters perhaps do.

Also, there’s some evidence Republican voters are more motivated in general by the Supreme Court than Democratic voters are. In the 2016 national exit poll, 21 percent of voters said that Supreme Court appointments were the most important issue to their vote, and they split 56-41 for Trump.

But let me pick a few nits with French’s claim. One questionable assertion is his idea that “a new Supreme Court pick will galvanize the entire [Republican] base for months.” That may understate how many other stories the Supreme Court pick will compete with for attention. The news cycle moves very quickly these days, and Trump’s nomination of Neil Gorsuch for the Supreme Court last year was a major news story for only a couple of weeks. The death of Antonin Scalia and the Republican refusal to consider Barack Obama’s nomination of Merrick Garland also did not gain much traction as a news story in the 2016 campaign given how much else was going on.

Perhaps, as the exit-poll data implies, the Supreme Court was an overlooked issue in 2016 that was more important to evangelical voters and other parts of the Republican base than the media assumed. But it was not necessarily a top-of-mind issue to these voters. The exit poll question specifically prompted voters to think about the Supreme Court. But when Gallup and other pollsters ask open-ended questions about what issues are most important, the Supreme Court doesn’t really register. Nor does abortion, for that matter — issues such as immigration and the economy are rated as being much more important.

Also, assuming Trump has his choice confirmed by the Senate before the midterms, the Supreme Court will arguably be more of a backward-looking issue in 2018 than it was in 2016. I say “arguably” because Kennedy probably won’t be the last justice to retire under Trump; liberals Ginsburg and Breyer are retirement risks, as is conservative Clarence Thomas. Still, in 2016, voters were deciding on an open Supreme Court seat and not just the prospect of further vacancies.

Finally, even if base motivation is crucial in midterm elections, it’s worth considering its effect on swing voters. In 2016, voters preferred Hillary Clinton’s prospective Supreme Court appointments to Trump’s. Despite that, Gorsuch was a reasonably popular nominee last year. But he was replacing another conservative justice, whereas a replacement for Kennedy could potentially produce a big ideological shift in the court. For instance, If Democrats can frame Trump’s nominee as threatening Roe v. Wade, they could find public opinion on their side, as voters oppose overturning Roe v. Wade by more than a 2-to-1 margin. The nomination is also coming against the background of a midterm election, and voters tend to view the ruling party skeptically at the midterms, seeking to elect members of the opposition party to check its power.

Argument No. 2: Kennedy’s retirement forces red-state Democratic senators to make a tough vote

Five Democratic Senators — Indiana’s Joe Donnelly, Missouri’s Claire McCaskill, Montana’s Jon Tester, North Dakota’s Heidi Heitkamp and West Virginia’s Joe Manchin — are up for re-election this November in states that Trump won by double digits in 2016. There’s also Alabama Democrat Doug Jones, who isn’t up until 2020 but who already has to carefully calibrate his positions in one of the nation’s reddest states. As the Washington Examiner’s Philip Klein argued, these Democrats are in a tough position:

The difficulty faced by red state Democrats is that even in a more conservative states, a substantial portion of their base is going to be fiercely anti-Trump, and opposed to any of his judicial nominees. At the same time, particularly in the very red states (Missouri, North Dakota, Indiana, and West Virginia) where Trump won big, it’s going to be really difficult to vote “no” on a qualified Supreme Court nominee.

While it won’t be an easy vote for any of these Democrats, especially so close to the midterms, there are also some mitigating factors for them. One is that other than Jones, all of the senators already voted on Gorsuch, with Heitkamp, Manchin and Donnelly voting aye and McCaskill and Tester voting nay. If in doubt, they could just vote the same way on Trump’s next nominee.

Another is that it could plausibly be to these Democrats’ advantage to demonstrate their centrist and independent streak by voting for Trump’s pick. Heitkamp, for instance, has already run ads bragging about how often she votes against Democrats and with Trump’s position. Sure, the Democratic base would be upset with her — but there aren’t a lot of Democratic base voters in states such as North Dakota, and almost all these states have already held their primaries anyway.

Finally, there’s one Republican who’s potentially put in a tough position by Kennedy’s retirement. That’s Nevada’s Dean Heller, who voted for Gorsuch, but who faces a tough re-election race in a state that isn’t known for its cultural conservatism. And unlike the Democrats, Heller’s vote could fairly easily prove to be decisive. Republicans don’t have much margin for error with only a narrow 51-49 advantage in the Senate, and they have possible issues with senators ranging from Maine’s Susan Collins (who might object to a nominee she saw as a threat to overturn Roe) to Arizona’s John McCain (who could miss the vote because of illness).

The Gorsuch nomination went well for Trump, but this one could be tricker

So the arguments for why Kennedy’s retirement could be a political boon for Republicans are persuasive — but only up to a point. And they seem to be using Gorsuch’s nomination as a template for how things will go this time around when that won’t necessarily be the case.

Gorsuch’s nomination was one of the most successful episodes of Trump’s presidency; he was a fairly popular selection with swing voters, but also one who pleased conservative activists. Republicans were also able to “nuke” the Supreme Court filibuster with relatively little backlash, perhaps in part because Democrats had already ended it for most other types of nominations.

Supreme Court nominations are not always cakewalks, however, as cases such as Harriet Miers and Robert Bork (and Clarence Thomas) attest. There are several potential risks to Trump and Republicans:

Trump could nominate a relatively moderate justice, in an effort to keep Collins and Alaska’s Lisa Murkowski on board and to put maximum pressure on red-state Democrats, but then face a backlash from conservatives.

Trump could nominate someone very conservative, but at the price of actually putting votes such as Collins’s and Murkowski’s at risk and of turning off swing voters.

Trump could nominate someone who had vetting issues, or someone who triggered a debate about qualifications, or someone who was seen as too much of a political crony. Historically, these sorts of justices have had trouble getting confirmed.

On balance, Kennedy’s retirement probably offers more political upside than downside for Republicans, but it’s a long way from a slam dunk. And this is not a White House where things always — or usually — go so smoothly as they did with the Gorsuch pick.