As America barrels toward a presidential election, control of the US House of Representatives is no longer Democrats’ biggest focus. Nor will retaining it be their hardest task; they have a more uphill battle to retake the US Senate. But even though the conventional wisdom so far is that Democrats will keep the House, it’s far from assured.

The 44 seats that won Democrats a decisive majority in 2018 are also the ones that will be the toughest for them to hang onto in 2020. These are the seats in America’s suburbs that typically elect Republicans, but trended blue as voters — particularly college-educated women — registered their displeasure with the Trump. Republicans need 18 or 19 seats on net (depending on the outcome of the special election in North Carolina’s Ninth Congressional District) to get back to a slim majority, but with another wave of GOP retirements, it’s looking difficult for them to pull off.

“The kind of district where the majority will be won or lost are in these outer suburban districts,” said Dave Wasserman, the US House editor for the Cook Political Report. “Judging by history, it’s going to be very difficult for Republicans to win back many of these Clinton districts that flipped in 2018.”

Once a party has reclaimed the majority in the House during a midterm year, history shows they typically keep it during the next presidential cycle. This could prove true in 2020, especially given the fact that President Donald Trump was a driver of the huge Democratic turnout in the 2018 midterms. Trump will quite literally be on the ballot in 2020, which could give Democrats another boost in legislative chambers.

But Democrats don’t just want to keep their House majority — they are looking at expanding it in more than 30 districts across the US. They’re playing aggressively in Texas after flipping two House seats there in 2018, and with a rash of Republican retirements — including the only black House Republican who narrowly hung on to his seat in 2018, Rep. Will Hurd — Democrats may finally have an opportunity to realize their dream of a blue Texas, or at least a bluer one.

“The DCCC started this cycle by going on offense, and the reality for vulnerable Washington Republicans of defending their deeply unpopular health care repeal agenda is setting in for Republican incumbents from Kenny Marchant to Will Hurd to Pete Olson,” DCCC chairwoman Rep. Cheri Bustos (IL) told Vox in a statement.

The National Republican Congressional Committee didn’t respond to a request for comment from Vox.

First Democrats must get through a possibly contentious primary season. Progressive groups like the Rep. Alexandria Ocasio-Cortez-aligned Justice Democrats have already announced incumbent targets, and the official campaign arm of House Democrats, the Democratic Congressional Campaign Committee, is aggressively pushing back.

The DCCC is also embroiled in internal turmoil, Politico reported last week. A wave of top staffers have resigned amid controversy surrounding Bustos, after many longtime lawmakers of color complained top DCCC staffing wasn’t diverse enough. The organization is looking for a new executive director while an interim leader fills in; an aide told Vox they’re planning to fill the position as soon as possible.

There are still many months to go, and even though Democrats’ House map is looking favorable, they don’t have it in the bag just yet.

House Democrats are playing defense in a lot of districts

House Democrats exceeded expectations when they walloped House Republicans in districts across the country in 2018.

The places where Democrats cleaned up were rapidly diversifying suburban districts outside major metropolitan areas. These were areas with college-educated voters who may have voted for Republicans in the past but didn’t like Trump. After two years of total Republican control in Congress, they wanted Democrats to put a check on the president and deal with a slew of issues like rising health care costs, passing universal background checks, and more.

“It is suburban districts that are diversifying and were largely drawn in aggressive gerrymanders [in 2010] to just be safe enough with the assumption the bottom wouldn’t fall out of the suburbs,” a DCCC aide told Vox.

On top of that, candidates that consistently did well in 2018 were women, often ones who had careers in the military or other public service. These were candidates who were not conventional politicians and had a message of cleaning up corruption in Trump’s Washington.

“People recoil at how Washington works, and they want people who are human,” the DCCC aide said.

Democrats pulled off a startling coup in seven California House districts long held by Republicans, took over four New Jersey districts after a wave of Republican retirements, and won four Pennsylvania districts once the state’s gerrymandered congressional map was redrawn after a state Supreme Court ruling.

Democrats’ wave was so strong they even picked up districts they thought furthest from their reach, like South Carolina’s First Congressional District. That district had been under Republican control since the 1980s, until Democrat Joe Cunningham beat Republican Katie Arrington by less than 4,000 votes.

But now, moderate Congress members like Cunningham have to make the argument that they came to Washington and actually did something — whether it’s holding Trump accountable or actually passing bills. To be sure, the House has been passing plenty of legislation by itself, but it’s had no luck getting those bills through the Senate, so the latter is a tougher argument to make.

The DCCC is concerned with defending 44 districts, including a wide swath of territory in California, New Jersey, and Pennsylvania, among other states.

Arizona’s First Congressional District — Rep. Tom O’Halleran California’s 10th Congressional District — Rep. Josh Harder California’s 21st Congressional District — Rep. TJ Cox California’s 25th Congressional District — Rep. Katie Hill California’s 39th Congressional District — Rep. Gil Cisneros California’s 45th Congressional District — Rep. Katie Porter California’s 48th Congressional District — Rep. Harley Rouda California’s 49th Congressional District — Rep. Mike Levin Colorado’s Sixth Congressional District — Rep. Jason Crow Connecticut’s Fifth Congressional District — Rep. Jahana Hayes Florida’s 26th Congressional District — Rep. Debbie Mucarsel-Powell Georgia Sixth Congressional District — Rep. Lucy McBath Iowa’s First Congressional District — Rep. Abby Finkenauer Iowa’s Third Congressional District — Rep. Cindy Axne Illinois’ Sixth Congressional District — Rep. Sean Casten Illinois’ 14th Congressional District — Rep. Lauren Underwood Kansas’ Third Congressional District — Rep. Sharice Davids Maine’s Second Congressional District — Rep. Jared Golden Michigan’s Eighth Congressional District — Rep. Elissa Slotkin Michigan’s 11th Congressional District — Rep. Haley Stevens Minnesota’s Second Congressional District — Angie Craig New Hampshire’s First Congressional District — Rep. Chris Pappas New Jersey’s Second Congressional District — Rep. Jeff Van Drew New Jersey’s Third Congressional District — Rep. Andy Kim New Jersey’s Fifth Congressional District — Rep. Josh Gottheimer New Jersey’s Seventh Congressional District — Rep. Tom Malinowski New Jersey’s 11th Congressional District — Rep. Mikie Sherrill New Mexico’s Second Congressional District — Rep. Xochitl Torres Small Nevada’s Third Congressional District — Rep. Susie Lee Nevada’s Fourth Congressional District — Rep. Steven Horsford New York’s 11th Congressional District — Rep. Max Rose New York’s 19th Congressional District — Rep. Antonio Delgado New York’s 22nd Congressional District — Rep. Anthony Brindisi Oklahoma’s Fifth Congressional District — Rep. Kendra Horn Pennsylvania Seventh Congressional District — Rep. Susan Wild Pennsylvania Eight Congressional District — Rep. Matt Cartwright Pennsylvania 17th Congressional District — Rep. Conor Lamb South Carolina’s First Congressional District — Rep. Joe Cunningham Texas Seventh Congressional District — Rep. Lizzie Fletcher Texas 32nd Congressional District — Rep. Colin Allred Utah’s Fourth Congressional District — Rep. Ben McAdams Virginia’s Second Congressional District — Rep. Elaine Luria Virginia’s 7th Congressional District — Rep. Abigail Spanberger Washington’s 8th Congressional District — Rep. Kim Schrier

Democrats’ offensive strategy, explained

Democrats’ 2020 offensive map is their unfinished business from 2018.

One lesson Democrats learned during the midterms is there were a number of districts not on their radar in 2018 that would have been easy to flip with a little more investment.

A perfect example of this is Texas’s 24th Congressional District, which touches suburbs in both Fort Worth and Dallas. Republican Rep. Kenny Marchant barely hung on to his seat in 2018, with little-known Democratic challenger Jan McDowell coming within three points of beating him after spending less than $70,000 on her race.

“This was on no one’s map in 2018, but Marchant won by three points against a Democrat who was ignored by the party in DC, and did great with hardly any money,” Wasserman told Vox.

Marchant just announced he will retire rather than run for reelection in 2020. He’s not alone; two other Texas Republicans have announced in recent days that they’re retiring.

They were “much less interested in being in the minority” for another two years, University of Texas at Austin government professor Jim Henson told Vox. “It’s just not very attractive to some of these Republicans to be looking at a very tough election fight.”

The 24th Congressional District is now squarely on the DCCC’s expansion list, along with five other districts. To underscore how seriously it’s taking Texas, the official campaign arm of House Democrats recently opened up a field office in Austin.

“It’s not an accident that so many Texas Republicans are suddenly retiring. Four months ago the DCCC responded to the energy on the ground and opened an office in Texas, placed six senior staffers on the ground, and deployed organizers in key communities across the state to lay the groundwork for victory next year,” Bustos said. “Clearly that investment is already paying off and Democrats are well positioned to compete in and flip more seats in Texas.”

Democrats are hoping more Republican incumbents see the writing on the wall in states beyond Texas. Looking at their expansion map in 2020, it’s clear their path to extending their majority (should they hang onto all or most of their frontline districts) winds through states where they won big in 2018 but could improve in 2020: Texas, Pennsylvania, New York, and New Jersey.

Here are the DCCC’s target districts for expansion in 2020. Retirements are noted in parentheses.

Arizona’s Sixth Congressional District — Rep. Dave Schweikert California’s 22nd Congressional District — Rep. Devin Nunes California’s 50th Congressional District — Rep. Duncan Hunter Colorado’s Third Congressional District — Rep. Scott Tipton Florida’s 15th Congressional District — Rep. Ross Spano Florida’s 18th Congressional District — Rep. Brian Mast Georgia’s Seventh Congressional District — Rep. Rob Woodall (Retiring) Iowa’s Fourth Congressional District — Rep. Steve King Illinois’s 13th Congressional District — Rep. Rodney Davis Indiana’s Fifth Congressional District — Rep. Susan Brooks (Retiring) Kentucky’s Sixth Congressional District — Rep. Andy Barr Michigan’s Sixth Congressional District — Rep. Fred Upton Minnesota’s First Congressional District — Rep. Jim Hagedorn Missouri’s Second Congressional District — Rep. Ann Wagner North Carolina’s Second Congressional District — George Holding North Carolina’s Ninth Congressional District — OPEN North Carolina’s 13th Congressional District — Rep. Ted Budd Nebraska’s Second Congressional District — Rep. Don Bacon New York’s First Congressional District — Rep. Lee Zeldin New York’s Second Congressional District — Rep. Peter King New York’s 24th Congressional District — Rep. John Katko New York’s 27th Congressional District — Rep. Chris Collins Ohio’s First Congressional District — Rep. Steve Chabot Pennsylvania’s First Congressional District — Rep. Brian Fitzpatrick Pennsylvania’s 10th Congressional District — Rep. Scott Perry Pennsylvania’s 16th Congressional District — Rep. Mike Kelly Texas’ 10th Congressional District — Rep. Mike McCaul Texas’ 21st Congressional District — Rep. Chip Roy Texas’ 22nd Congressional District — Rep. Pete Olson (Retiring) Texas’ 23rd Congressional District — Rep. Will Hurd (Retiring) Texas’ 24th Congressional District — Rep. Kenny Marchant (Retiring) Texas’ 31st Congressional District — Rep. John Carter Washington’s Third Congressional District — Rep. Jaime Herrera Beutler

There’s already drama over primaries

Establishment Democrats in Washington have a thorn in their side going into 2020: the threat of longtime Democratic incumbents being primaried by younger, insurgent progressives.

Groups like Justice Democrats that emerged in 2018 have stoked the ire of Democratic leadership. The group has already announced some of their Democratic targets in 2018: Reps. Henry Cuellar of Texas and Eliot Engel of New York are two prominent ones. Cuellar’s more moderate Texas district in particular will be an interesting experiment of whether a progressive can win.

“It’s a conservative district. We ran on an endorsement from the NRA,” Cuellar Campaign Manager Colin Strother told Vox. “The Justice Democrats have been spinning some yarn that Congressman Cuellar has been deceptive and if his voters only knew his record ... no, the voters are very aware of his voting record.”

The Justice Democrats didn’t successfully primary Democrats en masse in 2018, but they had a few notable success stories: Alexandria Ocasio-Cortez beat then-House Democratic Chair Joe Crowley in a remarkable underdog race in the Bronx and Queens. Crowley was widely seen as the heir to House speaker Nancy Pelosi’s throne someday, but he was suddenly out of a job when Ocasio-Cortez beat him in the primary. Ocasio-Cortez has since gone on to become one of the most well-known (if controversial) stars of the first-term class in the House.

In Boston, former Rep. Michael Capuano was primaried by Justice Democrats-backed candidate Ayanna Pressley, a Boston City Councilor and woman of color. Pressley has gone on to join Ocasio-Cortez and two other new congresswomen, Reps. Rashida Tlaib (MI) and Ilhan Omar (MN), as part of “the Squad,” a progressive group that has drawn fire from conservatives and President Trump.

As Vox’s Matt Yglesias wrote earlier this year, there’s a distinct theory of political change behind Justice Democrats’ move to primary moderate Democrats: Even if you don’t win the challenge, you hopefully force the moderate incumbent further and further to the left.

Their theory of political change works not because it’s likely that left-wing challengers will unseat dozens of incumbent House Democrats but because a handful of successful challenges will scare a wide enough swath of similarly situated incumbents into moving left. Justice Democrats ... while obviously critical of the existing party establishment is — by definition — an organization that is committed to the Democratic Party and working with and through it as a vehicle for change ... The point, however, is not to displace the Democrats but to change them.

The group has already been successful in shaking things up in Washington, DC. They’re hoping they can replicate some of that success in 2020.