There are wave elections, and there are wave elections. In 1894, for instance, the Republicans gained 130 seats in the House out of a total of 357 seats up for election. In 1932, the Democrats gained 97 seats out of 435. In 2010, the Republicans picked up 63 seats.
But all politics is local.
In Alabama’s 2nd District, for instance, the Republican won by 5,000 votes out of 216,000 cast in 2010, a margin of 2%. In Texas’ 23rd District, the Republican won by 7,000 votes out of 151,000 cast, and in the 27th District, the Republican won by 700 votes out of 105,000. In South Dakota, the Republican won by 7,000 votes out of 319,000. In Minnesota’s 8th District, the Republican won by 4,000 out of 277,000 cast.
So it went throughout the country, and so it went in all the wave elections. Waves occur from the aggregation of local politics, local elections, and a very large number of those local elections are not blowouts at all (though many are; some elections look like the losing candidate was just taking up space on the ballot).
In the coming 2014 mid-terms, the races in both the House and the Senate are similarly extremely tight, especially in the so-called battleground States. Indeed, even in wave elections, potsful of seats are locked up tight by the incumbent. See, for instance, the map presented here, showing gains and holds from the 2010 wave.
If the 2014 close races all break the Republicans’ way in the Senate, they could pick up 12 of the 6 seats they need to take control. If those races go the Democrats’ way, though, so would the wave go their way: they’d have 67 seats (counting the Independent and the Socialist who caucus with the Democrats) instead of their current 55.