We’re getting to the point in the primary season when people turn their focus to the general election. Since Hillary Clinton tore through the Northeast on April 26, the Bernie Sanders campaign has laid off staff and suffered fundraising setbacks. But Sanders has intimated that he will keep fighting, even contesting the Democratic convention in July. So, could Sanders damage Clinton’s chances in the general election? Do long, hard-fought primaries weaken the candidate who emerges from them victorious?

That question, which is probably even more pressing for Republicans this year, has preoccupied political scientists for decades. The hypothesis that divisive primaries are detrimental is intuitive: Candidates attack one another, dividing the party and alienating supporters. But research findings have been mixed.

In a 1998 study of presidential elections, University of New Mexico political scientist Lonna Atkeson challenged the theory by suggesting that divisive primaries occur when the party is already divided. In other words, divisive primaries are the symptom, not the disease. We’re in the midst of an open primary, but take recent incumbent presidents as an example: Gerald Ford in 1976, Jimmy Carter in 1980 and George H.W. Bush in 1992 ran into trouble in the general election, but not because they were challenged in the primaries. They attracted challengers in the primaries because they were already in political trouble. Controlling for factors that account for this political trouble — the strength of the economy and the president’s popularity — Atkeson found that the effect of divisive primaries on how well the nominee does in the general election drops out. In other words, divisive primaries don’t make the incumbent party vulnerable; the causation runs the other way.

The prolonged Democratic primary in 2008 renewed scholarly interest in the divisive primary question, and studies of that contest have produced conflicting results. Henderson, Hillygus and Tompson found in a 2010 paper that a Democratic primary voter who was “frustrated” with the primary was more likely to vote for Republican John McCain in the general election. But they also found that substantive political issues were a bigger factor in voters’ decision-making than primary-inspired angst. Clinton voters who supported the Iraq War, for example, were more likely to vote for McCain in the general. They concluded, as Atkeson did, that the impact of divisive primaries has more to do with different views within the party on political issues than the occurrence of the divisive primary itself.

In a 2010 paper, Todd Makse and Anand Sokhey looked at Ohio’s Franklin County, chosen because it’s representative of the American public as a whole, and found evidence in precincts that had been favorable to Clinton of “defection and abstention” in the general election — voting for McCain or not at all. Amber Wichowsky and Sarah Niebler in a 2010 paper looked at tone as well as competitiveness (the closeness of the contest between Obama and Clinton in different areas) and found that negative ads in the primary had little effect on Obama’s performance in the general election.

You could cherry-pick studies to argue that contentious primary races hurt a nominee, but even those effects are small. There just isn’t a compelling case that competitive primaries damage a nominee’s prospects.

It’s worth noting that it’s hard for observational studies to get at exactly what aspects of a “divisive” primary season might matter. Studies like Atkeson’s focus on relative divisiveness — a comparison of the percentage of the primary vote won by each party’s nominees (from that perspective, the Democrats may be in pretty good shape this year). The studies cited here don’t directly account for the length of the primary season as a driver of outcomes, but a longer primary is a necessary condition for the competition Atkeson identifies and the negative tone that Wichowsky and Niebler identify. And how long a candidate stays in the race, along with how competitive he or she is, still appears to be a primary factor that voters and the media weigh when considering whether a candidate should drop out.

The conventional wisdom that follows from the (questionable) assumption that competitive primaries are damaging to nominees is that candidates should drop out of the primary early and allow the party to coalesce around the front-runner. For both parties, the norm in effect has apparently been that major competitors should leave the nomination race before the convention — the earlier the better. These norms may be, as we’ve seen from the political science studies mentioned above, based on incorrect assumptions about how much a divisive contest matters. But the pressure is real nonetheless. We saw it in the 2008 Republican contest when Mitt Romney left the race and support consolidated around McCain. Clinton was also the recipient of this pressure in the 2008 cycle — very early on, before she went on to win a number of contests.

How much will this pressure matter to Sanders? Well, it hasn’t made a difference so far despite Clinton’s lead in delegates, pledged and super. But there are good reasons for Sanders to stay in. For one, he’s still putting victories on the board, including in Indiana on Tuesday. It also appears that the Sanders campaign plans to go to the convention this summer with an agenda for the party platform, and it’ll have a strong case for why his ideas should carry some weight. And because the evidence isn’t clear that a competitive primary is a hindrance in the general election, it’s hard to defend the argument that Sanders should have stepped aside by now.

Additionally, fellow Mischiefs of Faction writer Seth Masket has noted that ambitious, high-quality candidates tend to drop out early because they are likely to value their future ambitions within the party. But it’s not clear where Sanders’s relationship with the Democratic Party is going. Sanders, an independent U.S. senator from Vermont, caucuses with the Democrats but has eschewed their label. His candidacy has been about the future of the party, but it’s also been billed as a revolution and a social movement. Will Sanders act like the kind of candidate who wants to run for president again (not likely, given his age), to get on the VP short list or to secure a Cabinet position? For those wondering whether pursuing the Democratic nomination has brought Sanders into the party fold, the path he chooses will be instructive.

Sanders’s next move will also tell us which side he falls on in the debate that’s raging about how parties should work. If the purpose of parties is to let elites nominate the most ideologically reliable candidate who can unite the party and win in November, then it makes sense for party leaders to eliminate the risk of division. But if there is real value in letting voters — all primary voters — have a voice in the party’s decision, then party leaders may want to ride out a long primary season. Because the evidence about the impact of a divisive primary is inconclusive, the stakes of this tradeoff aren’t quite clear.