Bernie Sanders made reforming the Democratic Party platform the last big push of his presidential campaign, refusing to endorse Hillary Clinton until the party came around on his favorite policies.

This has long seemed like a logical endgame for Sanders, who has made pulling Clinton to the left a critical goal of his presidential run. This weekend, he won a string of additional platform concessions on several long-held policy goals. With those under his belt, he’s set to endorse her.

But did changing the platform actually change how the Democratic Party would govern? After all, though the platform outlines the key "ideas and beliefs" of the party, it doesn’t bind presidential candidates to any particular policy — and it’s not clear its leaders even look to it for guidance. (Bob Dole, the 1996 Republican presidential nominee, once famously declared that he’d never even read the Republican platform.)

Though it’s tempting to think of the platform as a throwaway, nonbinding document that only hardcore activists turn to, there are some surprising ways in which the party’s platform do matter, according to the political scientists who study such things.

I interviewed eight of those experts. Here’s what I learned.

The parties vote in line with their promises more than 80 percent of the time

Lee Payne, associate professor at Stephen F. Austin State University

A few years ago, Payne went through all of the platforms by both the Republican and Democratic parties from 1980 until 2004. He identified every "direct promise" in those platform — pledges he thought amounted to concrete policy positions — and then compared those promises with all of the votes taken on either the House or Senate floor.

"Reading through all of those platforms, I just wanted to rip my damn eyeballs out," he said, reflecting on the grueling legwork that went into his dissertation.

Despite the slog, what Payne found might stun some cynics: In 25 years, both Democratic and Republican lawmakers in Congress voted in accordance with their platforms 82 percent of the time.

Payne’s research, which didn’t look at the presidency, also found that members of both parties are far more likely to fall in line with the platforms now than they were in the mid-20th century.

One political science paper published in 1980, using the same criteria as Payne’s, found that Congress only voted with its platforms about 66 percent of the time from 1944 until 1976.

That number has skyrocketed for both parties, but especially for the GOP. Overall, Democrats in Congress voted for positions that matched their platforms 74 percent of the time in the past 30 years, while Republicans did so 89 percent of the time.

Either way, though, it’s clear that looking at either party’s platforms is a good way to guess how it will vote.

"Members of the House and Senate vote in line with the party platform at a very high rate," Payne says. "So, yes, I would say it matters."

International studies also show that parties try to make good on their promises

B. Dan Wood, political scientist at Texas A&M

Payne isn’t alone in finding that parties really do try to keep the pledges they make. In an email, Wood pointed to research also showing that parties are actually pretty good about working toward fulfill their pledges.

Wood cited an international review of existing studies, by French political scientists François Pétry and Benoît Collette, that found political parties fulfill 67 percent of their promises on average if elected. Eleven of the 18 studies looked at by the French researchers were about US politics.

The professors write:

Contrary to popular belief, political parties are reliable promise keepers. Why people underestimate the capacity of political parties to keep their election promises remains an open research question. Stories of broken party promises on a few important issues have considerably more readership appeal and salience in the public than the coverage of pledges fulfilled on many less important issues.

Wood also noted that separate research from 1990 also found a strong link between party platforms and those parties’ federal spending priorities.

"It is reasonable to say that political parties fulfill their promises most of the time," he writes.

The case for skepticism about the platform’s significance

Dave Hopkins, political scientist at Boston College

Terri Fine, political scientist at University of Central Florida

But just because parties tend to vote with the platform’s promises doesn’t mean we should necessarily expect them to make all-out pushes to reach their most consequential — or politically vulnerable — goals.

For one, parties have ways of quashing bills before they even make it to the floor for a vote. (Payne’s analysis only looks at bills that made it to a congressional vote.) And in our interview, Hopkins made the case that the platform can serve as an easy giveaway for presidential nominees looking to placate fired-up ideological activists — precisely because it lacks any real enforcement mechanism.

"The activists can get something of a free hand with the platform because they can be the only ones who care," Hopkins says. "And then the candidates will think, ‘Well, if this makes the activists happy, and nobody else is paying attention, then there’s no harm done.’"

Something similar appears to be playing out in the Democratic Party this year, Hopkins notes: Sanders loyalists are winning some concessions on the platform, and Clinton wants to ensure that they come aboard for November.

But those stances are unlikely to really hurt Clinton in a general election, where so much other noise can drown them out. (Hopkins noted that Clinton, like Dole, can also distance herself from some part of the party’s platform if she feels she has to.)

"There’s a lot of precedent for the platform to be controlled by the ideological activists," Hopkins says. "They’re the ones who care most about it."

His point gets to a more fundamental objection with putting too much stock in the platform fight: Sure, the parties can vote in line with their pledges. But presidential candidates in particular can distance themselves from any parts of it they find politically damaging, Fine says.

"The platform committee is there to represent the party faithful, but candidates run for themselves," Fine says. "If politicians don’t believe it or think it will somehow hurt their chances of winning with some segment of the electorate, they’ll easily dissociate themselves from it."

Party platforms track pretty closely to how the public views the presidential candidates

Elizabeth Simas, political scientist at the University of Houston

Leah Wright Rigueur, public policy professor at Harvard

Skeptics of the platform’s importance note that few voters actually read the platform, and that’s certainly true. (Some political scientists told me they weren't sure if most lawmakers even read the platform.)

Does that mean — regardless of its effect on Congress — that the voters themselves don’t care what it entails?

Research by Simas argues that’s not the case. The platforms really do appear to closely track with how the public views the two major parties — and that includes their presidential nominees, she said.

"Voters are in fact picking up on the parties' objective policy positions," she writes in a 2011 research paper with political scientist Kevin Evans. "The objective position of the party does affect voters' perceptions of both parties' presidential candidates."

To reach that conclusion, Simas and Evans compared the ideological positions of the platform with voter survey data on how the parties are perceived. They found that the more conservative a party’s platform in any given year, the more likely the public was to consider that party’s nominee a conservative.

I’m somewhat skeptical of the idea that this isn’t being driven by the perception of the presidential candidates themselves, rather than how the public sees their party platform. And Simas allowed in our interview that it’s impossible to know "which way the directional arrow is running."

But even if the platform is not causing voters to think a certain way about the candidates, Simas’s research draws a convincing connection between public attitudes about the parties and the platforms over the past 30 years.

That means the Democratic Party’s recent movement on its platform should help shore up its left flank. But it also suggests there may be a real political downside for presidential nominees who let their bases dictate too much of the platforms, notes Wright Rigueur.

"It can be something that helps underscore a larger campaign or attack point," she says. "There’s a balance between the issues they think they can incorporate and then stuff they worry can be used in a political campaign [against the nominee]."

Platforms as a reflection of how the party is changing

Jennifer Victor, political scientist at George Mason University

Ryan Enos, political scientist at Harvard

If the platforms are useful for understanding how voters change their minds, they’re also useful as windows into the jostling for power between the smaller factions that together form the parties.

"The coalitions come up with this written statement, and that is useful to figuring out what all these folks can agree on together," Victor says. "We’re really looking at the party written on paper."

This is the lens through which Victor has studied party platforms. In one study, she tried to figure out which organizations — like Planned Parenthood, veterans groups, or Jewish advocacy groups — tended to do the best in getting their preferred language onto the Democratic Party platform.

These were also the grounds on which Enos also defended the value of the platform — as containing the stated objectives of the Democratic Party, and therefore one of the best ways to gauge the party's overall direction.

Platform proposals may got shot down, or be included on the platform and later ignored. But just by being aired, they can gain currency and support among lawmakers.

"We know that voters in the public get pulled in the direction of the people with the microphone," Enos says. "If someone gets up there and tries pulling some issue to the left, the party can move in that direction."