If Republicans are to win the Senate, they probably are going to have to do something they haven't done since 1980: beat more than two Democratic Senate incumbents in November.
In that Reagan Revolution election - one of the best for the Republican Party in its entire history - the GOP flipped 12 seats held by a Democratic incumbent who sought another term. The Republicans defeated nine Democratic incumbents in the November general election, and they won three other Democratic-held seats where the incumbent who held the seat ran for reelection but lost an earlier primary.
Incredibly, in the 16 Senate elections since then, the Republicans have flipped only 12 Democratic Senate seats where the incumbent was running again: It's taken them three decades worth of elections to match the achievement of that single 1980 effort.
In recent times, Republicans have had some good Senate elections, like in 1994 - when they netted eight seats and took control of the upper chamber - as well as 2004 and 2010, when they netted four and six seats, respectively. But these were electoral triumphs built mainly on winning Democratic seats where incumbents were not running: In 2010, for instance, Republicans made their six-seat gain largely in open seats: The only incumbents they beat were then-Sens. Blanche Lincoln (D-AR) and Russ Feingold (D-WI).
Click here for a Table that shows the number of seats that switched parties in post-World War II elections, along with whether an incumbent was running in the seat or whether it was open.
Source: Vital Statistics on Congress, Crystal Ball research
In this timeframe, Democrats have flipped more Senate seats held by incumbents than Republicans, an average of 2.7 per cycle vs. 2.1. That advantage gets starker, though, after 1980: Democrats have flipped more than triple the number of Republican seats where an incumbent was running for reelection, 38 for them versus just 12 for the Republicans. That includes two very big years for Democrats where they took control of the Senate largely through the defeat of incumbents: They won seven seats in states where an incumbent Republican ran for reelection in 1986 to flip the chamber, and then netted their six-seat gain and slim 51-49 majority in 2006 by exclusively beating incumbents.
This is pretty clearly a trend, and one that's been largely ignored in analyses of this year's Senate elections. Yes, most people who follow politics know that it's hard to beat a Senate incumbent: The postwar reelection rate for senators is 80%. But the clear Democratic edge in beating incumbents, and the Republicans' recent inability to rack up big numbers of incumbent defeats in any election since 1980, is a largely hidden hurdle they face this November.
It seems unlikely that beating only two Democratic incumbents will be sufficient for a Republican majority this year, though it's not impossible. Let's game it out:
First, let's assume that Republicans hold all of their current seats, most notably a competitive open seat in Georgia and embattled Senate Minority Leader Mitch McConnell's (R) Kentucky seat.
As we've been writing for months, the best Republican pickup opportunities in the Senate are in Montana, South Dakota, and West Virginia. The latter two are open seats, and the Big Sky Country seat is held by an incumbent, albeit an appointed one: Sen. John Walsh (D). Let's give the Republicans these three seats in this hypothetical scenario, which has them flipping two seats where the incumbent is retiring and one where the incumbent is running. That's one incumbent defeat and a net gain of three seats so far, halfway to the six needed to win the majority.
The next four most vulnerable seats are held by incumbent Democrats in Alaska, Arkansas, Louisiana, and North Carolina, all Toss-up races. Remember, under this scenario, Republicans have to take the Senate and only beat two incumbents. So let's say that Republicans only manage to beat one of these four incumbents: Sen. Mark Pryor (D-AR).
That leaves Republicans capped out at two incumbent defeats and a net gain of four seats, with only two remaining targets where the incumbent is not running: Iowa and Michigan, where Sens. Tom Harkin (D) and Carl Levin (D), respectively, are retiring.
We list both races as Leans Democratic right now, with Iowa trending toward the more competitive Toss-up category and Michigan perhaps trending away, given the small but clear polling lead established by presumptive Democratic nominee Rep. Gary Peters and the state's inherent Blue tilt in federal races: A Republican hasn't won the state in a presidential or Senate contest in 20 years. There are no other open Democratic-held Senate seats.
A Republican path to a 51-49 Senate majority that features the party beating incumbents in just Arkansas and Montana and then sweeping the Democratic open seats in Iowa, Michigan, South Dakota, and West Virginia is a possible path but not a very plausible one. So it appears that in order to win the Senate, the Republicans will have to break their three-decade drought of beating just two or fewer Democratic incumbents in any midterm or presidential election year since 1980.
The list of states with potentially vulnerable Democratic Senate incumbents is a long one: Alaska, Arkansas, Colorado, Louisiana, Minnesota, Montana, New Hampshire, North Carolina, Oregon, and Virginia. Republicans are clear favorites in the aforementioned Montana seat, but are probably no better than 50-50 in any other incumbent-held seat. Indeed, if Pryor as well as Sens. Mark Begich (D-AK) or Mary Landrieu (D-LA) were not running again, those seats would very likely be easy pickups for the Republicans because the seats are so fundamentally Republican at the federal level in this era. But the presence of these formidable incumbents is likely going to force the GOP to surmount their recent poor history in targeting Democratic Senate incumbents.
In an election where the big-picture fundamentals seem to be pointing their way, Republicans have some obscure but relevant history to overcome.