Everyone knew that the 2014 Senate election was going to be a tough one for Democrats, in large part because they were defending more seats than Republicans, and many of those seats were in red states. And of course, Democrats lost all the close races, with the exception of the one in New Hampshire. This is going to have an effect on the Democratic caucus in the Senate that we haven't really been talking about since last Tuesday: it's going to make it more liberal. In fact, the red state Democratic senator is a nearly extinct species.
Look at the incumbents who lost: Mark Begich in Alaska, Mark Pryor in Arkansas, Mark Udall in Colorado, Kay Hagan in North Carolina, and possibly Mary Landrieu in Louisiana, who is headed for a run-off. That's three red-state senators, and two from swing states. Democrats also lost vacated seats in Iowa (swing), Montana (basically red), South Dakota (red), and West Virginia (red).
If Landrieu loses, there will be no more Southern Democratic senators. None. The only Democrats left in the Senate representing red (or perhaps reddish) states will be John Tester in Montana, Claire McCaskill in Missouri, Joe Donnelly in Indiana, and Joe Manchin in West Virginia.
For a long time the conventional wisdom has been that red-state Democrats might be a pain in their party's behind some of the time, breaking with them on important issues and generally bad-mouthing the party and its leadership, but there's really nothing to be done about it. Because the Senate gives inordinate power to mostly conservative small states—fewer than 600,000 Wyomingers get the same two senators as 38 million Californians—Democrats have no choice but to go to red states to assemble a majority. But what if that wasn't actually necessary?
Let's look at the 2016 elections. The new Senate will have 54 Republicans and 46 Democrats, meaning that Democrats will have to take either 4 or 5 seats to win control (depending on who wins the White House, and thus whose vice president would break the tie if it were 50-50). Is that a possibility? It is indeed. Not only will Republicans be defending many more seats than Democrats, a number of them will be in blue states. Seven GOP senators—Mark Kirk in Illinois, Ron Johnson in Wisconsin, Kelly Ayotte in New Hampshire, Chuck Grassley in Iowa, Pat Toomey in Pennsylvania, Rob Portman in Ohio, and Marco Rubio in Florida—will be running in states Barack Obama won twice. Except for Grassley (who'll be 83 in 2016 and might retire), they all won their seats for the first time in the GOP's midterm 2010 sweep, and will have a much harder time facing the electorate in a presidential year. Furthermore, every Democrats up for reelection in 2016 is in a state Obama won twice.
That means that it's entirely possible that two years from now, the Democrats could take control of the Senate without a single ornery Southern Democrat who feels the need to criticize the party and "distance" him or herself from its leaders. The closest thing to centrists left in the caucus would be Donnelly and Manchin. It would be, for all intents and purposes, a true blue majority.
Would such a majority be fragile? Sure. If a Democrat (Hillary Clinton or someone else) wins the White House, 2018 would be a midterm in which the out-party, still Republicans, would probably have a good year, and control might swing back. And of course, there will be future Democrats running in the South, who will presumably be a lot like the generation now departing.
In any case, this election has furthered the geographic polarization of the parties, and 2016 could make it even clearer.