The simplest way to understand the Democrats’ chances is to start with the races they’re likely to win. If they pick up all the GOP-held seats that the Cook Political Report rates as already leaning their way, they will net around 16 seats. That means they need to win only around eight more to net the 23 seats they need for the majority.

The reason Democrats appear so well positioned to do that is that the battlefield is very wide. They merely need to net those additional eight seats out of dozens and dozens of contests. Cook rates 29 GOP-held seats as “Toss Ups” — meaning Democrats need to win only a third of those — and another 29 as “Lean Republican,” which in this environment are also in play. That’s a total of nearly 60 seats.

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Many of the seats that are already leaning Democratic are in districts that were carried by Hillary Clinton in 2016 or are highly educated or suburban or more racially diverse. Many of the Toss Ups are also in more educated and suburban areas, though Democrats are also trying to expand into more exurban and rural districts, where they have also fielded candidates, which has also broadened the map.

I spoke with Dan Sena, executive director of the Democratic Congressional Campaign Committee, about his view of the map, why he thinks Democrats have multiple paths to the majority, and the big question that keeps him awake at night. An edited and condensed version of our conversation follows.

PLUM LINE: What’s the prediction?

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DAN SENA: One of the key strategic pieces that we put into place is a battlefield that can produce a narrow victory or a larger victory. There are probably about 15 to 20 races that would immediately come our way. Sitting behind them is another 20 to 30 where we are either down a couple points, tied or up a point or two. The key question is: How will those races break, and in what direction?

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PLUM LINE: The low-hanging fruit are mostly districts that Clinton won, that are highly educated and suburban?

SENA: Seventy-five percent of them are well-educated, suburban or heavily diverse districts.

PLUM LINE: What characterizes the “Toss Up” districts?

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SENA: These are all districts with a unique feature that gives the Democrat an advantage, because the environment, or the strength or history of the candidate, has put races in play that Republicans didn’t see coming. It’s a smattering of different types of districts.

PLUM LINE: [President] Trump’s closing argument must have worked in some places and not in others. Can you get granular on where the migrant caravan, birthright citizenship and so forth are working for them and where they aren’t?

SENA: Every time he does something, there’s an equal and opposite reaction someplace. When he’s doing that, it helps us in California and the Chicago suburbs — races like Illinois 6 and 14 move towards us. It helps us in Northern Virginia. It remains to be seen what that type of conversation does in North Carolina, in more rural Illinois, in some of the more rural Texas seats.

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We designed our strategy so that regardless of what he did, we would be able to maximize opportunity someplace else on the battlefield. In some of the more rural districts in Ohio and Texas, or even Washington 5 — where you have higher white populations — those could become more challenging.

PLUM LINE: There’s been talk that Democrats have been so focused on health care that they haven’t directly engaged Trump’s attacks on immigrants. I’m trying to get a sense of where the equal and opposite reaction you’re talking about comes from.

SENA: The reaction has to do with everything that Trump does, not just immigration. He is in the background of all of this regardless of the issue he’s talking about.

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PLUM LINE: What about turnout among young voters and Latinos?

SENA: Millennials are already voting at [rates] that are knocking on the door of 2016. Look at California — the percentage of the vote share that Hispanics are making up is knocking on the door of 2016. [Both groups] are already going to make up a larger share than they do traditionally in any midterm cycle. We’re seeing the same with African Americans in Florida and Georgia.

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Will that hold on Election Day? That’s why we’re spending $30 million to make sure they get out and vote.

PLUM LINE: In your polling, are you finding that a lot of these Republican incumbents are at a perilously low point? The Upshot’s polling has a lot of them hovering at around 45 percent.

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SENA: In many, yes. But we also have many where we’re up by like two, and we’re knocking on the door of 50 and they’re at like 48.

PLUM LINE: What’s the nightmare scenario? What has to go wrong big time for it not to come together?

SENA: The biggest question that keeps me up at night is: When Trump engages the base, what actually happens? I don’t think anybody really knows. When he engages, and there are larger shares of people voting on both sides, it becomes less predictable. We tried to build a system that would account for reaction to Trump in both a positive and negative way.

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PLUM LINE: Are there any surprise expenditures in districts that we don’t know about?

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SENA: We spent several hundred thousand dollars in places like New York 27, California 50, Alaska [at large], Iowa 4, Ohio 7 — in very red areas.

PLUM LINE: What’s the most likely outcome?

SENA: I think we can win the House narrowly, and I think we can win it by a little more than narrowly. The point was to create a series of paths that get us there. We have invested in 80 districts across the country. The scope of the battlefield is unparalleled.