Will Nancy Pelosi be speaker of the House when the new Congress convenes in January? Last week, 16 incoming Democratic House members circulated a letter announcing that they will vote for “new leadership in both our Caucus meeting and on the House Floor,” adding, “We promised to change the status quo, and we intend to deliver on that promise.” Yesterday, nine of the letter-signers doubled down on their threat to block Pelosi unless she agrees to rules reform. A handful of other Democrats who did not sign the letter had previously said they would oppose Pelosi becoming speaker again.

If these numbers hold, it will be game over for Pelosi. With all 435 members voting, she needs a majority of the chamber, or 218 votes, to become speaker. With 233 incoming Democrats and three House races still undecided, she can afford to lose only 15 Democratic votes. Pelosi’s opponents hope to force her out of the race, allowing another — as yet unnamed — Democrat to step in.

But Pelosi is adamant that she will stick it out and win. In a news conference last week, she goaded potential opponents: “Come on in, the water’s fine.”

Why is Pelosi so confident? We can find clues in past speakership fights.

1. Opponents need to do more than sign letters

It’s not easy to orchestrate an insurgency. As the 19th century turned into the 20th, progressive Republicans — frustrated by the grip of Speaker Joseph Cannon (R-Ill.) on the floor agenda — sought to overthrow the speaker. Like today’s rebel Democrats, they circulated a petition calling for a change and gathered enough signatures to prevent Cannon from gaining the 218 votes needed to hold the speakership.

But when the time came to rally behind a rival candidate, the insurgents fractured. Without any organization that could coordinate around a single candidate or enforce his opponents’ commitment to vote as a bloc, Cannon picked off enough dissident Republicans to keep his majority. Pelosi is adopting a similar strategy. Last Wednesday, she persuaded Rep. Brian Higgins (D-N.Y.) to reverse course after he had signed the letter opposing her candidacy. Asked about his flip, Higgins said, “There’s no alternative right now, and there’s not going to be one.” With their numbers eroding, Pelosi’s remaining foes may be looking to cut a deal.

The House Freedom Caucus’s 2015 rebellion offers a better road map for success. After threatening to depose Speaker John A. Boehner (R-Ohio), the Freedom Caucus held together to provide the pivotal votes to select his replacement on the House floor. First, they rejected the leading contenders for being too close to the party establishment. Next, they backed a dark-horse candidate, Rep. Daniel Webster (R-Fla.). Then they threw their votes to their preferred candidate, Rep. Paul D. Ryan (R-Wis.). Their numbers gave them leverage, but their organization ensured they could wield it.

2. Pelosi holds both carrots and sticks

Pelosi has a hefty arsenal of tools to secure support from wavering members. When Rep. Marcia L. Fudge (D-Ohio) considered challenging Pelosi, she folded quickly. Her price? Pelosi promised to restore a key House panel on voting rights and make Fudge its chair.

Pelosi wields sticks as well. Dissidents could face retribution if they fail to oust her. If Pelosi can hold on to the speakership, she will have the power to withhold fundraising support and desirable committee assignments from her detractors. Pelosi’s opponents need the ability and will to protect one another if they lose. Without a robust organization, that is hard to do.

Consider again the 1909 bid to unseat Cannon. When the progressive Republicans failed, Cannon reassigned dissenting committee chairs to the worst committees, including the infamous Committee on Ventilation and Acoustics. But when the Republican Party endorsed primary challenges against Cannon’s opponents, the dissidents channeled surplus campaign funds to their electorally endangered colleagues and barnstormed in their districts. Similarly, members of the House Freedom Caucus insulated themselves from party punishment by cultivating a network of donors outside of the Republican Party campaign fundraising apparatus.

In both cases, organization gave the dissidents resources to defend themselves against retribution, limiting party leaders’ ability to punish them by knocking them out of their seats.

3. You need some big guns

For an insurgency to succeed, you need powerful allies who can shield vulnerable members. Most of Pelosi’s challengers are first-term members or lawmakers with little seniority. Most senior Democrats, including the likely heads of the major committees and prominent liberals, are backing her. Even former president Barack Obama has endorsed Pelosi.

Progressive Republicans in the early 1900s realized they had a similar problem and encouraged senior colleagues to join the fight. Rep. William Hepburn (R-Pa.), a dyed-in-the-wool Republican and long-standing committee chair, allowed insurgents to use his committee room as a war room, which emboldened some hesitant members to join the cause. But so far, no Hepburn equivalent has stepped up — making it unlikely that wavering critics of Pelosi’s leadership will join the challenge.

4. Careful what you wish for

Even if Pelosi becomes speaker, don’t expect smooth sailing. While Rep.-elect Alexandria Ocasio-Cortez (D-N.Y.) has defended Pelosi’s progressive record and endorsed her candidacy, she also called for the party’s incoming progressives to form “a sub-caucus” along the lines of the Freedom Caucus. If they can garner enough members to stop House Democrats from securing the 218 votes needed to control the floor, this group could dictate terms to party leaders — much like their conservative counterparts.

Such a move could replace the large — but not terribly disciplined — Congressional Progressive Caucus with an organization capable of enforcing lawmakers’ commitment to negotiate and vote together. If properly organized, Democratic dissidents would find themselves able to pursue the sorts of measures many of them ran on — complicating Pelosi’s time as speaker.

Ruth Bloch Rubin is an assistant professor of political science at the University of Chicago and author of “Building the Bloc: Intraparty Organization in the U.S. Congress” (Cambridge University Press, 2017).