Republicans are on their way toward a takeover of the U.S. Senate, according to FiveThirtyEight's Nate Silver, who released the site's first election forecast Sunday morning.

Silver, whose fame grew during the 2012 presidential election, gives Republicans about a 60 percent chance of re-taking the Senate.

Republicans need to swing six seats to re-capture Senate control. They're on track to win in West Virginia, South Dakota, Montana, and Arkansas, according to Silver. Four states are toss-ups — Louisiana, North Carolina, Alaska, and Michigan. The most likely path to victory, then, for Republicans is swinging the four seats in which they're favored and winning two of the four toss-up seats. Polls have continued to show a large Republican advantage in states with open Senate seats.

There are also three Democratic-leaning seats — in Colorado, New Hampshire, and Iowa — the GOP could plausibly win. In the end, Silver said, Republicans could swing as many as 11 Senate seats. Then there's the caveat — Republicans are facing significant challenges in Georgia and in Kentucky.

You can read Silver's whole forecast here, and watch his appearance on ABC's "This Week" below: