Last month, we published an election preview identifying factors that hint for or against a blue wave this November. We posed these questions: Will the historical trend of wave elections get the Democrats over the 218-vote threshold in the House? If so, will they make it to 230? What about 250? And what about the Senate? What gets done in 2019 will depend on the margins. Sweeping policy changes are much easier to pass in the House with 250 votes than with 225. Just think back to the passage of the Affordable Care Act (when Democrats controlled 257 seats). Thus, watching races that point to the size of a potential blue wave can help us predict what 2019 has in store.

House Races to Watch

As it stands now, Democrats are predicted to flip the House. The Cook Political Report on October 8 listed 13 House races as “likely Democratic,” 12 as “lean Democratic,” two as “Democratic toss-ups,” and 29 as “Republican toss-ups.” If Democrats win all those races, in addition to the 182 seats considered solidly Democratic, that gets them to 238 votes. However, to have the overwhelming majority that Democrats achieved in the 2008 election (257), they will have to flip some “lean Republican” and even some “likely Republican” seats. As we continue to watch the trends now through election night, here are the races we are paying particular attention to as bellwethers for the final margin:

VA-10 Comstock (R) vs. Wexton (D): It is hard to imagine the Democrats taking the House without defeating Republican Barbara Comstock, who is trailing her opponent by seven points. It is a lean Democratic race in a district that Hillary Clinton won in 2016 by ten points. If Democrats fail to pick up that seat, predictions of a blue wave are likely overblown.

IL-06 Roskam (R) vs. Casten (D): If Democrats win Illinois’ 6th District, it is a strong indicator that they could reach 230 votes in the House. The race is a toss-up, with Roskam leading by just one point – and the district went to Clinton by seven points in 2016. If Roskam loses, it is likely that other Republicans in similarly tight races will lose as well.

GA-06 Handel (R) vs. McBath (D): Karen Handel’s race in Georgia is currently rated as leaning Republican, though President Donald Trump won the district by less than two points in 2016. If McBath manages to unseat Handel, who currently leads by four points, Democrats have a shot at achieving a 240-vote hold on the House.

MI-06 Upton (R) vs. Longjohn (D): If House veteran Fred Upton loses in Michigan’s 6th District, we are looking at a blue wave of 2008 proportions. It is a likely Republican seat in a district Trump won by eight points, and Upton currently leads by four. If Democrats can win there, they have a real shot at crossing the 250-vote threshold.

What about the Senate?

As we noted in last month’s election preview, the Senate is a toss-up. While a blue wave might take the House, it is not unprecedented for a party to gain seats in one chamber and lose seats in the other. In 1982, for example, with a Republican president hovering around 40% approval, Democrats gained 27 House seats and lost a Senate seat. This year could have a similar outcome, because the electoral map is heavily tilted against Democrats, who are defending 26 seats compared to the Republican’s 9. Even so, Democratic voter enthusiasm may carry the day. If Democrats can defend their red state incumbents, they may have a shot at flipping vulnerable seats such as those in Nevada, Tennessee, and Arizona.

What does polling tell us?

It depends. If we learned anything in 2016, it’s that polling is an art, not a science. Not only can polls be wrong, they can be consistently wrong. If the polls are making assumptions about turnout that end up being incorrect, the polling numbers may not capture reality. Simply put, any race that’s close to the margin of error should be considered a toss-up even if polls have shown one candidate consistently ahead. Many races are still too close to call. Here are the ones we’re watching:

Florida, Indiana, Missouri, Montana, North Dakota, and West Virginia: Democrats are trying to hold onto seats in each of these states that Trump won in 2016. If one or two of them turn red, it is almost certain that Republicans will maintain control of the Senate. Democrat Heidi Heitkamp in North Dakota faces the toughest challenge from Republican Kevin Cramer, who currently leads by nine points. Joe Manchin holds a healthy lead in West Virginia (though his decision to support Brett Kavanaugh’s nomination could depress his Democratic support), and the other races are currently within the margin of error. For Democrats to hold these seats, incumbency advantage and voter enthusiasm will need to overcome the partisanship of the state.

Nevada, Arizona, and Tennessee: Democrats are targeting vulnerable Republican Dean Heller in Nevada and open seats in Arizona and Tennessee as possible seats to flip. All three are toss-ups and within the margin of error, with the Democrat slightly ahead in Nevada and Arizona. If Democrats are going to win a majority, it will likely involve flipping one or more of these seats.

Texas and New Jersey – Really?: For years, Democrats have dreamed of turning Texas blue, and they may have a shot. Challenger Beto O’Rourke is currently six points behind Republican Ted Cruz in a state Trump won by nine points in 2016. Still, for Democrats to take Texas, voter turnout will have to drastically exceed historic trends. Thus, if Texas goes blue, it is almost certainly taking control of the Senate with it. At the same time, Democrat Robert Menendez’s seat in New Jersey was recently called into question with a handful of polls showing his lead in the low single digits. Though Menendez now sits at plus seven, a shocking loss of a seat not considered in play would be disastrous for Democrats hopes of taking the Senate.

Unpredictably Remains

Of course, many factors remain unpredictable as we head into the last month before the election. The battle over Kavanaugh’s nomination has certainly animated the Democratic base, but there is evidence that Republican intensity has been galvanized as well. Any surprising changes to the President’s travel schedule (like last month’s announcement of plans to visit Texas, which has long been a solidly red state) in the coming weeks could indicate which races aren’t going as planned. And as always, President Trump – and his impact on the electorate – is a wildcard.