Republicans have a two-in-three chance to maintain control of the Senate, according to new forecasts published Wednesday by FiveThirtyEight.

Two of FiveThirtyEight’s three prediction models give the GOP a two-thirds chance to hold the Senate, where Republicans currently have a 51-49 advantage. A third model is slightly more confident in the GOP, giving the party a 70-percent chance to keep control of the upper chamber.

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FiveThirtyEight’s prediction models include a “lite” model that considers only state and national polling and a “classic” model that considers both polling and other factors, such as fundraising, past voting and historical trends. Another model, the “deluxe” forecast, considers expert opinions in addition to everything the “classic” model takes into account.

The Democrats have about a 16 percent chance to add two seats in the Senate, according to the classic model. That would give the party a 51-49 advantage. The party has an 11 percent chance to add three seats and a 6 percent chance to add four seats, according to the same model.

The model also gives the Democrats a 17 percent chance to add one seat, which would create a 50-50 split in the Senate that would favor the GOP because Vice President Pence would have the tie-breaking vote.

There is about a 16 percent chance the GOP keeps its 51-49 majority, about a 12 percent chance the GOP adds one seat and an 8.5 percent chance the GOP adds two seats, according to the classic model.

There are 35 Senate seats up for grabs this election. FiveThirtyEight rates 18 of them as solidly Democrat, five as likely Democrat, three as leaning Democrat, two as toss-ups, two as leaning Republican, one as likely Republican and four as solidly Republican.

And while the Democrats are unlikely to win back the Senate, the party still sees a narrow path to victory.

FiveThirtyEight also currently gives the Democrats better than an 80 percent chance to win back control of the House, according to the website’s House forecast.