As we enter the 2020 election year, there are three questions looming over American politics: 1. Who will Democrats pick as their presidential nominee? 2. Will that person be an acceptable alternative to a highly polarizing President Trump in the right combination of states to reach 270 electoral votes? 3. Will Republicans hold the Senate or will Democrats take over next year?

This week, we'll focus on the last of those questions, because should Democrats win the presidency, they may immediately confront the reality that there's a real limit to what they can accomplish without a Senate majority. Conversely, if Trump is reelected, a Republican majority in the Senate would further enable him to lock in a conservative federal judiciary for decades to come, among other things. Say what you want about Trump, but he already has left a lasting imprint on the judiciary that will last long after he goes back to Mar-A-Lago.

When talking about the Senate, it is important to be careful using words like “majority” and “control.” The terms are hardly interchangeable. A majority means 51 seats (50 if a party also holds the White House), which grants them committee and subcommittee chairmanships and nominal control of the Senate floor, but with real limits. It takes a supermajority of 60 seats, or even 67 in some matters, to have real control of the chamber.

The Senate has changed enormously from the days when its members were elected by state legislatures. In recent decades, the Senate has devolved into little more than a smaller version of the House, the major difference being that each state enjoys equal representation. But the less distinctive nature of the Senate has not diminished its influence. It still limits the power of a presidency—even one with a House majority.

On a very superficial level, the Senate picture in 2020, with 23 GOP seats up to only 12 for Democrats, is the opposite of 2018, when Democrats had 26 seats up to just nine for Republicans. But there is one big caveat. In 2018, Democrats defended 10 seats in states carried by Trump, including five by 19 or more points, while the GOP only had a single seat up in a state carried by Hillary Clinton. This time, Republicans are defending no senators from deep behind enemy lines. Indeed, the only seat held by either party in a state that leans strongly to the other side is Democrat Doug Jones in Alabama, who understandably faces a very stiff reelection challenge.

Republican incumbents Susan Collins in Maine, Cory Gardner in Colorado, Martha McSally in Arizona, and Thom Tillis in North Carolina all face daunting races, but none quite so tough as the ones faced two years by Joe Donnelly in Indiana, Heidi Heitkamp in North Dakota, and Claire McCaskill in Missouri, all of whom ended up losing.

In a good night for Democrats, they could beat two or three from the group of Collins, Gardner, McSally, and Tillis, but to beat all four, they would need a national political wave comparable to 2018. Should any of the four Republicans survive, Democrats would then need to pick up the open seat in Kansas, win one of the two seats up in Georgia, or beat Joni Ernst in Iowa or John Cornyn in Texas.

Can Democrats win a Senate majority in November? Their chances are about one-in-three. It’s a bit more likely that they net a seat or two, getting to 48 or 49 Senate seats.

Meanwhile in the House, the most likely outcome is one of only modest change. Republicans are somewhat better positioned simply because Democrats, in their 40-seat gain in the 2018 midterm elections, have 30 seats up in districts that Trump carried, compared to Republicans holding just three seats in districts where Hillary Clinton prevailed.

That disparity is partially offset by two factors: First, a new congressional district map in North Carolina effectively gives Democrats two seats. Second, a political environment provides Democrats a bit more of a tailwind. The RealClearPolitics generic congressional ballot test gives Democrats an 8-point advantage, while Nate Silver’s FiveThirtyEight and last month’s NBC News/Wall Street Journal poll both indicate a 7-point Democratic edge. With 27 vacant or open GOP seats to 11 open Democratic seats, few of those GOP seats are in competitive districts, making that disparity less important than it might appear. Republicans need a 20-seat net gain to retake the majority lost in 2018. That's a much taller order than them hanging onto the Senate.

This story was originally published on on January 3, 2020

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