With former Gov. Brian Schweitzer (D-MT) deciding to pass on the open seat in Montana, the odds of a Republican takeover have increased, according to Nate Silver, a political analyst with an uncanny ability to predict elections.

Republicans already had a fair chance to take control of the Senate before Schweitzer’s surprising announcement this past weekend. But with six seats currently held by Democrats in traditionally red states, three of which will be open seats, the odds are beginning to look favorable for Republicans.

“The G.O.P.’s task will not be easy: the party holds 46 seats in the Senate, and the number will very probably be cut to 45 after a special election in New Jersey later this year,” wrote Silver at FiveThirtyEight. “That means that they would need to win a net of six contests from Democrats in order to control 51 seats and overcome Vice President Joseph R. Biden Jr.’s tiebreaking vote.”

“A race-by-race analysis of the Senate, in fact, suggests that Republicans might now be close to even-money to win control of the chamber after next year’s elections,” adds Silver. “Our best guess, after assigning probabilities of the likelihood of a G.O.P. pickup in each state, is that Republicans will end up with somewhere between 50 and 51 Senate seats after 2014, putting them right on the threshold of a majority.”

Silver predicts that Republicans will lose the seat in New Jersey, but pickup the open seats in Montana, South Dakota, and West Virginia. That would give them 48 seats. He also gave Republicans even odds to pickup Arkansas and Louisiana, where incumbent Democrats, Sens. Mark Pryor and Mary Landrieu, are vulnerable.

But Silver notes that Democrats have slightly better odds at holding onto seats in Alaska and North Carolina, where Republicans lack top-tier challengers against Sens. Mark Begich and Kay Hagan.

Nate Silver: GOP could take control of the Senate in 2014