Not much, according to Sean Trende:
Any outcome we’ll see is likely to be roughly consistent with the underlying electoral fundamentals — a Democratic president’s low job approval rating, a tepid economy, a bad playing field for Democrats in the Senate and a good one in the House. Back in the winter, when “fundamentals”-based models were being produced, people were predicting Republican gains in the Senate in the range of six-to-eight seats, with error margins putting us in something of the four-to-10 seat range. This seems to be where we are headed.
But the upshot of this is that we can’t make grand predictions about 2016 and beyond. If 2014 was well-predicted by fundamentals (as were 2008 and 2012), we should continue to expect that elections will be well-predicted by fundamentals; we should prefer a parsimonious explanation to a more complex one. It is Republicans substantially over-performing or under-performing that might be meaningful, not Republicans getting what we’d expect, given the circumstances.
But, in Nate Cohn’s estimation, if Tuesday “night ends with tight races in Iowa, North Carolina, Colorado and Georgia, as the polls suggest, then the results will not be as great for Republicans as many analysts will surely proclaim”:
If there were a time when the Republicans ought to be making inroads into the Obama coalition, this should be it. The economy remains mediocre in many respects; there is turmoil in much of the world; and the American public is decidedly downbeat about the state of the country under Mr. Obama. His approval ratings have sagged into the low 40s. A significant proportion of Democratic-leaning voters say they disapprove of his performance.
Historically, presidential ratings like these have permitted the party that does not hold the White House to make substantial gains. This year, however, Democratic Senate candidates in the battleground states have largely reassembled the coalition that supported Mr. Obama two years ago. Democratic candidates would probably win Colorado, North Carolina, Iowa and Georgia — along with control of the Senate — if those who vote were as young, diverse and Democratic as they were in 2012 or will be in 2016.
The Dish 