In an interview with Jon Karl on ABC's "This Week," Silver, who recently relaunched his FiveThirtyEight franchise, gave Republicans a 60-percent chance of winning a Senate majority during the 2014 midterm election cycle.
But Democrats, who have in the past lauded Silver for his analysis of polls, on Monday were skeptical of his projection this time around.
"Nate Silver and the staff at FiveThirtyEight are doing groundbreaking work, but, as they have noted, they have to base their forecasts on a scarce supply of public polls," DSCC Executive Director Guy Cecil wrote in a memo Monday. "In some cases, more than half of these polls come from GOP polling outfits."
In 2012, Cecil noted, Silver incorrectly predicted Republican candidates would win in Montana and North Dakota, where Democrats ultimately triumphed.
"In fact, in August of 2012, Silver forecasted a 61 percent likelihood that Republicans would pick up enough seats to claim the majority," Cecil added. "Three months later, Democrats went on to win 55 seats."
The DSCC seemed to give more weight to Silver's latest prediction in a fundraising pitch to supporters Monday, however, calling it "shocking" and "scary."
Silver has often found himself on the receiving end of politically driven attacks from Democrats and Republicans alike -- but he drew particular ire from the GOP during the 2012 presidential election, when Silver cast doubt on Mitt Romney's chances to win the presidency as Election Day neared. Silver's state-by-state prediction in the presidential contest was ultimately 100-percent accurate.