If there’s an abiding lesson from 2016, it’s that national public opinion in the presidential race is not as important as the votes of individual states. Republican Donald Trump won by taking 304 electoral votes to Democratic nominee Hillary Clinton’s 227, even as Clinton beat him by 2.9 million votes and 2.1 percentage points nationally.

In 2020, Democrats will be looking to recapture states Trump won that went for Democrat Barack Obama in 2008 and 2012. And many of those states will also be prime battlegrounds in the fight for control of the Senate, where Democrats need a net gain of four seats to take a majority (three if they win the White House and the vice president can break 50-50 ties), while Republicans need a net gain of 19 seats to retake the House.

A look at the most competitive states in the East is below. These links will take you to the most competitive states in the Midwest, the South and the West.

Maine

As one of just two states that splits its electoral votes by congressional district, Maine will be a key presidential, Senate and House battleground. (The other state, Nebraska, is less interesting since the entire state voted the same way in 2016.)

Clinton won the popular vote in Maine by 3 points. She carried the 1st District by 15 points, while Trump carried the 2nd District by 11 points, which earned him one of the state’s four electoral votes. The Trump campaign is banking on holding on to the 2nd District, but Democrats see it as a place they can target, especially with a high-profile Senate race next year.

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The different presidential results here underscore America’s partisan realignment along regional lines. The 1st District, represented by Democrat Chellie Pingree, is much more liberal and densely populated. It includes Portland and affluent coastal communities along the southern shore and midcoast. Farther north, the 2nd District, represented by freshman Democrat Jared Golden, is sprawling and rural, encompassing potato country and the Downeast coast. While Democrats had held the seat for two decades, it elected a Republican in 2014. After voting twice for Obama, the district swung in 2016 to Trump, whose populist, anti-establishment message resonated with its mostly white, working-class residents.

Golden put the seat back into Democratic hands last fall, defeating two-term Republican Bruce Poliquin in the nation’s first use of ranked-choice voting at the congressional level. A Marine veteran and former committee staffer for GOP Sen. Susan Collins, Golden ran as a moderate who supports gun rights. (He was one of the few Democrats who voted against a background check bill that passed the House this year.)

Poliquin had led Golden by less than a point after Election Day 2018, but the Republican failed to surpass 50 percent of the vote. That triggered the state’s ranked-choice voting system, which has voters rank candidates in order of preference. If no one receives a majority, votes cast for the last-place finisher are allocated to the voter’s second choice. The process continues until someone secures more than 50 percent of the vote.

Golden beat Poliquin by just over a point in the ranked-choice voting tabulation. Poliquin contested the results, and the constitutionality of the entire ranked-choice voting system, but eventually dropped his challenge and has ruled out running for his old seat in 2020. The GOP field is still developing. But running in a district that Trump carried by double digits, Golden will face a competitive race that Inside Elections rates Tilt Democratic.

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The marquee race in Maine is likely to be the Senate race. Maine is a top pickup opportunity since it’s one of only two states that Clinton won where a Republican senator is up for reelection. Collins has relied on a moderate, independent brand to easily win her previous reelections. But her vote to confirm Brett M. Kavanaugh to the Supreme Court energized the left, and her eventual Democratic challenger will be able to tap into a nearly $4 million war chest amassed from contributors angered by that vote. National Democrats are excited about the candidacy of state House Speaker Sara Gideon, who outraised Collins during the third quarter of 2019. Gideon still faces a primary against a former gubernatorial candidate.

Collins has voted with Trump the least often of any GOP senator this year — 85 percent of the time, according to CQ Vote Watch. But her challenge will be convincing moderates who have supported her in the past that she can still be an independent check on the president, despite supporting his Supreme Court nominee. At the same time, she needs conservatives who turn out to vote for Trump to continue to vote Republican down-ballot, and not abstain from voting in the Senate race. Inside Elections rates the race Tilts Republican.

Pennsylvania

With its 20 electoral votes up for grabs, Pennsylvania is sure to be a top presidential battleground in 2020. Trump won the Keystone State by less than a point in 2016, garnering just 44,000 more votes than Clinton. Democrats are optimistic about their chances here, especially considering Obama won the state by 5 points in 2012 and 10 points in 2008.

Pennsylvania is still evenly divided when it comes to politics, with one senator from each party and a House delegation that is split between nine Democrats and nine Republicans. Democrats do have an advantage in voter registration, with nearly 48 percent of voters registered with the party. Republicans make up 38 percent of registered voters, while 14 percent are registered as independents or with other parties.

In some parts of the state, longtime registered Democrats who are more socially conservative have backed Trump. The president’s “drain the swamp” message and criticism of trade deals appealed to blue-collar workers, especially union members. Trade will likely be an election factor in the state again, along with health care, which is a top issue for voters across the country.

Democrats believe they can win over some Trump voters with an economic message focused on boosting the working class. Whether that message will resonate depends on the messenger, so the political environment in Pennsylvania remains in flux until Democrats choose a nominee. Former Vice President Joe Biden. has staked his nomination on defeating Trump in states like Pennsylvania. Biden has roots in Scranton, and his presidential campaign is headquartered in Philadelphia.

Democrats found success in Pennsylvania in 2018. Sen. Bob Casey easily won a third term, defeating GOP Rep. Lou Barletta, a close Trump ally, by 13 points. Democrats also flipped four GOP-held House seats. But they were helped by retirements in competitive seats as well as a new congressional map that resulted from a state Supreme Court ruling.

Pennsylvania does not have a Senate race in 2020, but it could have a handful of competitive House races. Two Republicans are in competitive contests, according to Inside Elections. Pennsylvania Rep. Brian Fitzpatrick, whose 1st District includes the Philadelphia suburbs, is one of two GOP House members in the country running for reelection in a Clinton district. He is a top Democratic target, but Democrats have yet to field a clear challenger there.

GOP Rep. Scott Perry, whose 10th District includes Harrisburg, the state capital, is in a seat that Trump carried by 9 points. Last year, with roughly 40 percent of the district new to him due to the new House map, Perry won reelection by just 3 points. And this year Democrats landed a top recruit in state Auditor Eugene DePasquale, who narrowly carried the 10th District in his 2016 race for auditor.

Democratic Reps. Matt Cartwright and Conor Lamb are both running in districts Trump would have carried in 2016 under the new map, so they could face competitive races. Lamb won a high-profile special election in a 20-point Trump district in 2018, but under the current lines, the president would have won by just 2 points. Both do not yet have clear GOP challengers.