Polling guru Nate Silver reinforced this point on Monday, suggesting that a lot of the statewide public polling is tailored to 2006 and 2008 turnout patterns - which would skew the number in favor of Democrats significantly. "It's also conceivable that some likely voter models based on past voting histories are overrating the propensity of Democrats to vote," Silver wrote. "If likely voter models are benchmarked to 2006 and 2008 patterns, therefore, they could underestimate the turnout gap, giving too much credit to Democrats who voted in 2006 or 2008 but who don't ordinarily." Silver now predicts that Democrats lose 53 seats in the House. So who are the Democrats who could be vulnerable if the GOP wave gathers full steam on Tuesday? The Cook Political Report on Monday put four more incumbent Democrats -- most of whom weren't considered vulnerable until very recently -- into its Toss Up column: Reps. Chellie Pingree (Maine), Mike McIntyre (N.C), Jim Oberstar (Minn.) and Rich Boucher (Va.). The Report also moved Rep. Mike Michaud (D-Maine) from Likely Democrat to Lean Democrat. Other possible seats that could be vulnerable to a big wave include the open Rhode Island seat vacated by Rep. Patrick Kennedy (D) as well Reps. Solomon Ortiz (D-Texas), Bob Etheridge (N.C.), Maurice Hincey (N.Y.), David Loebsack (Iowa) and Bruce Braley (Iowa). Even Rep. Barney Frank (D-Mass.) is facing a difficult challenge and is under 50 percent in recent polling.