US midterm elections are held every four years, and they’re a major test for sitting presidents. If a party loses control of Congress, it’s more difficult to advance the president’s agenda.

Historically, the party in the White House loses seats in the midterms. The trend was upended in 2002, when the party of President George W. Bush gained a few seats in the House and Senate, thanks to aggressive campaigning.

Since World War II, House seats have generally changed hands in midterms when the president’s approval rating is below 50%. In recent years, this has been particularly true of Democratic presidents.

In 2018, there was a strong blue wave in many states, with the Democratic Party winning seats in a record-breaking number of districts. This was led by Democratic candidates increasing their share of the vote, and many of them winning seats previously held by Republican candidates.

Some voters voted less than usual, but the overall turnout was high: nearly half of eligible Americans turned out to vote in 2018. Voter participation was much higher than it has been for midterms in 100 years and is the highest level for a midterm since 2014.

Among voters with annual family incomes of more than $150,000, Democrats won by an overwhelming margin (65% to 30%). This was the largest majority for any party in any race, and was largely driven by strong turnout of high-income voters.

There were also some surprising wins for Democratic candidates in races that were not expected to be competitive. For example, Sharice Davids, the joint-first Native American congresswoman from Kansas, increased her vote share in her district by 13% and won a seat that had been held by a Republican.

This was a large swing towards the Democrats, but in many districts, it wasn’t enough to overcome challenges from the Republicans. For example, West Virginia’s 3rd district flipped from Republican to Democratic, but a strong turnout by young and Latinx voters was not sufficient to make the difference in this race.

Abortion, immigration and other social issues dominated the national political debate this year. These issues drove turnout and the votes of many Democratic congressional candidates, especially in suburban areas and urban centers.

The president’s approval rating typically reaches a low in the first midterm after a new administration takes office. In the first midterms of Presidents Bill Clinton in 1994 and Barack Obama in 2010, they both saw their approval ratings sink to below 50%.

Despite this, some of the president’s key policies, including the expansion of government-run healthcare programs, protection of abortion rights and tightening gun control, were able to survive. But the Democrats lost control of Congress in both chambers and will need to work harder to defend their policies if they want to keep them alive.

The next two years will be critical to the future of US politics. If the Democrats can hold onto both chambers, they will be in a strong position to pursue their agenda. If the Republicans take control, they will be able to stall or even reverse many of President Biden’s policies.

After a historic midterm election, Democrats defied historical trends and President Donald Trump’s approval ratings to gain control of the United States Senate. They did so by a combination of resurgent political power and voter disdain for the President’s extremist policies.

In addition to winning a net of four state legislative chambers, Democrats held losses in several other states to a minimum, a remarkable feat of political defiance that is unprecedented for a president’s party in midterm elections. This holds the promise of boosting Democratic congressional and presidential majorities, but it also means that many more Americans will live in states run by partisan trifectas for the first time since World War II.

The Democrats’ success this year was driven by a combination of factors: weak Republican candidates; concern about the Supreme Court’s recent ruling overturning abortion rights and the backlash against Trump’s election denialism; and the party’s shift into a populist position that voters perceived as appealing to middle-class voters. These factors helped fuel a series of competitive races that saw a wave of Democrat wins in red and blue states.

For example, Pennsylvania Democrat John Fetterman upset a conservative candidate for the Senate seat of Pat Toomey, who had been appointed to fill out Biden’s term in 2016. In another race, Democrat Seth Magaziner beat a longtime Republican politician in Rhode Island’s Second Congressional District, an area that Biden won by more than 15 points.

A few of these newcomers, however, were unable to convey the shift in rhetorical tone that had been a key component of the Democratic campaign. In the Senate, for instance, a number of incumbents who might have struggled against an ideologically extreme Republican candidate in previous cycles, such as Colorado’s Michael Bennet or California’s Kamala Harris, did not even try to distinguish themselves from their opponents by aligning with the Party’s new populist economic platform.

These messengers did not perform well, and many voters felt that the Party’s messaging was faulty. This contributed to the Party’s reversal of fortunes, with the Electoral College tipping toward the Democrats’ favor by nearly two points.

The party also lost ground in a number of battleground states, including Florida, Ohio and North Carolina. But it kept its strongholds in Massachusetts, Maryland and likely California as well as a number of other states that are traditionally Democratic or lean blue.

By retaking the Senate, Democrats prevented President Trump from confirming his picks for federal agencies and the judiciary, a process that is typically fraught with legal challenges from the President’s political opponents. It also slowed Trump’s efforts to replace the Supreme Court and thwarted any plans to launch a wide-ranging investigation into possible crimes by the former President and his campaign team.

In the House, Democrats won a net of seven seats, but they lost five in competitive districts. Nevertheless, they have gained three veto-proof supermajorities and are likely to retain a majority in the next Congress.

These results suggest that the Party will need to be more consistent in conveying its populist message and addressing the issues voters care about most. This will likely require more than simply reviving its signature policy initiatives of the Obama administration, such as free college tuition and the enhanced Child Tax Credit.