The Democrats have betrayed their base. That’s the consensus on the left wing after the party agreed to a deal that reopened the government without resolving the fate of Dreamers, the millions of undocumented immigrants who were brought to the United States as children. “Democrats have drawn the wrath of a fired-up activist base that now feels betrayed,” Mother Jones’ Tim Murphy reported. Ezra Levin, a co-founder of Indivisible, told Murphy “there need to be repercussions for selling out Dreamers and broadly selling out progressive policy priorities like this.”

New York Times columnist Michelle Goldberg argued that in making this deal, which keeps the government open for another three weeks, Senate Majority Leader Chuck Schumer sold out the resistance, the mass movement that has been fighting Donald Trump’s presidency and fueling the Democrats’ success in special elections. “The energy of the progressive grass roots should be seen as a valuable resource for Democrats,” Goldberg contends. “If Donald Trump’s election taught us anything beyond the salience of white nationalism among our fellow citizens, it’s that passion matters, and that people respond when they see a leader who is willing to champion them even when it’s risky.”

This narrative is not just overstated, but rests upon a false understanding of the nature of the party itself. On the substantive issues, the shutdown deal has much to recommend to it: In exchange for three more weeks of budget funding, Democrats got a six year renewal of CHIP, a program that provides health insurance to nine-million low-income children, as well as a promise from Senate Minority Leader Mitch McConnell to hold an immigration vote within three weeks. McConnell’s promise might be of limited value, but if he reneges, Democrats can force another shutdown.

These machinations weren’t simply a matter of horse-trading, but reflect the fundamental nature of the Democrats as a heterogeneous party held together by a belief in government. In trying to balance the interests of Dreamers with those of CHIP recipients, Schumer wasn’t betraying the Democratic base or its activist base, but rather was taking into account that he serves a coalition of disparate groups. The millions of low-income families that rely on CHIP are as much a part of the Democratic base as activists who are pushing, rightly, for a law to protect Dreamers.

The Democratic base is much more diverse than that of the Republicans. According to a 2015 Pew poll, Republicans are strongly supported by Mormons, white evangelical Protestants, white Southerners, white men without college education, white people in general, and those between the ages of 69 and 86. These groups overlap significantly; Mormons are overwhelmingly white, for instance, and southern whites are often evangelical Protestants. By contrast, the core Democratic groups include blacks, Asians, religiously unaffiliated, post-graduate women, Jews, Hispanics, and millennials. These groups overlap less, and often have very different social and economic profiles; for example, black Americans have a high rate of church membership, while millennials don’t.

In short, the Republicans are the party of white conservatives, a very large and cohesive group. The Democrats are the party of many smaller groups that are opposed, for different reasons, to the politics of white conservatives.

The fundamental demographic differences between the two parties means that it is much harder, for better or worse, for the Democrats to follow the dictates of an ideologically militant wing. While a group like the Tea Party can remake the Republican Party, forcing it to acts of folly like the 2013 shutdown, Democratic activists will always be just one part of the Democratic coalition. (Some journalists conflate the Democratic base with the resistance—or, even less accurately, with Bernie Sanders supporters. “Democrats in Split-Screen: The Base Wants It All. The Party Wants to Win,” The New York Times wrote last June, referring to Sanders supporters, at best a minority faction, as “the base.”)

If the Democrats are heterogeneous, they are held together by a few core beliefs, one of which is a faith in government policies to improve people’s lives. This is why the Democrats have trouble getting what they want out of a government shutdown. An anti-government figure like Texas Senator Ted Cruz can pursue a shutdown with glee, as he did in 2013. Someone like Schumer, who wants the system to work, will always be reluctant to use a shutdown as a negotiating tactic.

The differences between the two parties also explains the type of leaders they produce. Being more ideological cohesive, the Republicans gravitate toward figures like House Speaker Paul Ryan, an ideologue, and McConnell, a partisan who is willing to pursue extremist tactics (as he did when he blocked President Barack Obama’s Supreme Court nominee Merrick Garland). Democrats, by contrast, prefer pragmatic dealmakers like Schumer and House Minority Leader Nancy Pelosi.

The fragmented nature of the Democratic Party also means its easier for Republicans to play the game of divide and conquer, as McConnell did by presenting the Democrats’ shutdown politics as a choice between CHIP recipients and Dreamers:

In the current political environment, where the GOP controls the White House and both houses of Congress, Republicans can set the terms of political battles and the Democrats are forced to play defense. By engineering a short shutdown, Schumer found a way to stick up for Dreamers and also win renewed funding for CHIP. Whether this was a shrewd or unwise tactic is up for debate—a lot of debate—and the coming weeks will deliver a verdict. But there’s no debate that Democratic politicians need to take into account the needs of all of their constituents, which includes low-income Americans and federal employees as well as Dreamers. It would be a grave mistake for the party to believe that the only way to defeat the Republicans is to become equally single-minded and extremist.