Charlie Cook: “The Senate is increasingly less a case of whether Democrats will take a majority, but how large will it be. The chances of the GOP keeping its losses down to a seat or two are dropping; I am thinking that a five- or six-seat gain is becoming highly possible. The three most likely GOP incumbents to lose are Martha McSally in Arizona, Cory Gardner in Colorado, and Thom Tillis in North Carolina. Right on the bubble are Joni Ernst in Iowa, Susan Collins in Maine, and both Georgia seats. A touch back from that are Steve Daines in Montana and Lindsey Graham in South Carolina, as well as the open seat in Kansas. All three states are likely to be won by Trump, so look for a possible repeat of 2016, when every Senate race went to the same party that won the presidential race there—the first time that had happened since the start of direct Senate elections in 1914.”

“What I am wondering is if this will be one or the rarest species of national elections—a wave election in a presidential year ending in a zero, meaning it will reverberate for a decade thanks to the coming redistricting. There are not a dozen Republican Senate seats that could fall, as Democrats suffered in 1980, but Joe Biden may well replicate Ronald Reagan’s 10-point victory over President Carter. The odds are it will be a bit less, perhaps in the 53 to 44 percent range, with 3 percent going to independents and write-ins, half of the number from four years ago.”