The idea of Democrats retaking the House and maybe even the Senate in what the media has dubbed a "blue wave" is so ingrained in the public consciousness that a prevailing sentiment (especially among hopeful Democrats) is that it's all but inevitable?
But is it?
A comparison between polling now and recent midterm elections suggests otherwise.
The RealClearPolitics average of "generic ballot" polls gives Democrats a 6.2% advantage, down from a whopping 13.1% edge on December 30th. By way of comparison, in the last "blue wave" midterm election--2006--Democrats led by an average of 12.7% in all polls conducted in April.
That was actually up significantly from the 9.4% average lead Democrats enjoyed in polls conducted in December of 2005.
12 years ago, when Democrats won five seats in the Senate and 31 in the House to retake control of both chambers, their advantage on the generic ballot increased by 3.3% from December to April. Today, it has shrunk by 6.9%.
In 2010, the last time a new President (Barack Obama) faced his first midterm and a Republican voter base motivated by the passage of the Affordable Health Care Act, the out-of-power Republicans held a slim 2.5% generic ballot advantage in December of 2009.
By April of 2010, that lead shrunk to just 2.0%.
There was essentially no movement in the polling average between December and April, yet by November of 2010, Republicans won six seats in the Senate and a whopping 63 in the House--the single biggest midterm victory since 1938.
Surprisingly, in April of 2014--seven months before another Republican wave election--Democrats held a 2.5% lead on the generic ballot.
This, too, was virtually unchanged from December of 2013, when Democrats held a 2.2% lead.
This lack of movement belied another Republican wave that November, as the GOP retook the Senate by winning nine seats and gained another 13 seats in the House, giving Republicans their largest Congressional majority since 1928.
Republican under-performance on the generic ballot ahead of a midterm in which they performed very well is also nothing new. In 2002, the last time a new Republican President (George W. Bush) faced his first midterm election, the out-of-power Democrats enjoyed a 3.8% generic ballot advantage of polls conducted in April.
RealClearPolitics does not keep records of polling from December of 2001, but in January of 2002, the Republican lead was 0.1%.
That November, Republicans defied all expectations and actually picked up seats in the House and Senate, even retaking control of the Senate in a development pollsters didn't see coming.
Could a similar Republican surprise be coming this November? It's certainly possible.
The generic ballot is, of course, an imperfect measurement of public sentiment ahead of a midterm election since it doesn't account for the partisan makeup of individual races and voter enthusiasm, but it is a helpful gauge of broad party preference.
Given the longstanding trend of a new President's party performing very poorly in that President's first midterm, Democrats must still be considered heavy favorites to perform very well in the 2018 elections, but recent midterm history suggests that the much-hyped "blue wave" is far from inevitable.