Donald Trump is a historically unpopular president, and Republicans in Congress are pushing through a remarkably unpopular agenda. Under such auspicious circumstances, it’s only natural for ardent Democrats to feel energized and empowered. Some see 2018 as their own Tea Party moment to sweep even the bluest of candidates to victory in the reddest of districts. It looks like an election Democrats can’t lose—the sort Americans haven’t seen since, well, last year.

So how can Democrats ensure that 2018 delivers the success they failed to achieve in 2016? The stakes are too high to rely entirely on one side’s enthusiasm or the other side’s disenchantment. If their overriding objective in 2018 is to save the country, not realign the Democratic Party, Democrats need to look back to the last time they won back the House in 2006. We helped coordinate that effort, and the lessons we learned then still apply today. Waves don’t happen on their own: Democrats need a strategy, an argument, and a plan for what they’ll do if they win.

In the last 60 years, control of the U.S. House of Representatives has changed hands just three times, always in midterm elections, with control shifting away from the president’s party. The 1994 and 2010 campaigns were dominated by attacks against the incumbent president and his party over health care; 2006 became a referendum over the ruling party’s incompetence and corruption. In percentage terms, the worst midterm defeat in the past century came in 1974, when a nation weary of obstruction of justice sent a quarter of the House Republican caucus packing. Some presidents are unfortunate enough to face one of these circumstances; with the midterms still more than a year away, Donald Trump already seems to have all those bases covered.

Opposition parties, by contrast, find the odds forever in their favor. In the last 20 midterm elections, the president’s party has picked up seats only twice: in 2002, when Republicans gained eight right after 9/11, and in 1998, when Democrats gained five thanks to House Republicans’ obsession with impeachment.

Trump and his party have particular reason to fear a reckoning in 2018. No first-term president has gone into a midterm this unpopular since Harry Truman lost 55 seats in the House and 12 in the Senate in 1946. Like Democrats in 1994 and 2010, Republicans in 2018 face a firestorm over health care. If Hurricane Katrina, Iraq, and the Jack Abramoff scandal dogged congressional Republicans in 2006, Trump is already torturing them with incompetence and corruption of unprecedented scale. Add potential electoral devastation to the list of Trump mistakes Republicans can’t prevent. Donald Trump came to Washington to make waves—and he may deliver a wave election powerful enough to sweep his party out of control of Congress.

Democrats enter the cycle with a distinct advantage. For campaigners in chief, the toughest race to win is when they’re the name in voters’ sights but not the name on the ballot. Trump will be an exceptional liability on the campaign trail—determined to redeem himself, desperate for validation from his base, and toxic to every candidate in a marginal race. Trump presents vulnerable Republicans with a no-win proposition: They can’t run with him and their Democratic opponents won’t let them run without him. The last thing a majority of voters want is to give this president a blank check—or as Trump prefers to call it, loyalty.

So Democrats don’t need to spend the next year navel-gazing over how to motivate their base. In 2018, Trump will provide the greatest fundraising and get-out-the-vote machine the party has ever had. Wave elections are a chance to build on that base by winning back voters disappointed in the other side. Democrats will have plenty of disappointments to bring to their attention, including Republican health-care and tax-cut plans that betray the working-class voters who put Trump in the White House.

To pull that off, though, Democrats must channel their anger, not be defined by it. In 1994, Gingrich Republicans used an alternative agenda, the Contract with America, to take back the House for the first time in 40 years. In 1998, those same Gingrich Republicans played to their conservative base by campaigning for impeachment, producing another historic result: making Bill Clinton the first president in 176 years to gain House seats in the sixth year of his presidency. Democrats should heed that same lesson. They don’t have to make 2018 a referendum on Trump’s impeachment. If they want to win the majority they need in order to hold Trump accountable, they’ll do much better making the election a referendum on Trump’s record.

That referendum will be won or lost in swing districts—and they are much harder to find than they used to be. The Cook Political Report found that the number of swing seats—where neither party runs more than 5 points better than it does nationally—has dropped by more than half over the last 20 years, from 164 to 72. The most vulnerable seats in the current House majority belong to 23 Republican incumbents in districts Hillary Clinton carried, largely clustered in the suburbs of major metropolitan areas like Los Angeles, Philadelphia, and Washington. These districts tend to be mainstream in tone and interest. That’s a tough place to win the hand Trump has dealt Republicans of cutting student aid, denying climate change, and eliminating protections for pre-existing conditions.

But Democrats don’t just need to choose the right battles, they also need to choose credible candidates who can win them. Candidate quality may not make the difference in a place like Montana’s at-large district, where Greg Gianforte won handily just hours after assaulting a reporter. Winning hotly contested swing seats, however, requires candidates who closely match their districts—even if they don’t perfectly align with the national party’s activist base. In 2006, the Democratic base was energized and angry, but then as now, capturing a majority required winning some tough races in red and purple states across the heartland. As leaders in that 2006 effort, we recruited a football player in North Carolina, a businessman in Florida, an Iraq veteran in Pennsylvania, and a sheriff in Indiana. The Democratic Party won twice as many seats as it needed to gain control.

There’s a long-term payoff for a party that gets this right. Good candidates not only help build a wave, they help sustain it. Wave elections offer the chance to establish new beachheads in hostile territory, but it takes gifted leaders to survive when the pendulum swings back. In the 1980 Reagan landslide, Republicans gained 34 House seats—only to lose 26 seats two years later—and 12 Senate seats, only to lose 8 senators and Senate control when those seats came open six years later. With the right candidates, the impact of a wave can be felt for decades. Half a dozen “Watergate babies” elected to the House in 1974 went on to serve in the Senate. So have three Democrats who joined the House in the 2006 wave.

Even with the right candidates in the right districts, a wave won’t get far without a credible plan to address the country’s problems, not simply run attack ads against the parade of horribles from the other side. In 2006, we published a book called The Plan, which offered detailed proposals on college, retirement, health care, and the economy. One reason today’s congressional Republicans are struggling to enact an agenda is that unlike the Contract-with-America Republicans of 1994, the GOP waves of 2010 and 2014 were built only on saying no to Obama.

Donald Trump may hand Democrats the election next year, but Democrats should strive to earn the people’s trust on their own merits anyway. These are serious times for a country at the mercy of an unserious president. The damage may take years to repair, and voters deserve to know what Democrats are going to do about it.