The repubs were rewarded for shutting down the government in 2013.
From October 1 to October 17, 2013, the United States federal government entered a shutdown and curtailed most routine operations because neither legislation appropriating funds for the fiscal year 2014 nor a continuing resolution for the interim authorization of appropriations for fiscal year 2014 was enacted in time.
A typical six-year itch midterm election suffered by most second-term presidents, this election saw the Republican Party retaining control of the House of Representatives and winning control of the Senate, while furthering their gains in the governorships and state legislatures . Because of these Republican gains, the election was commonly cited as a "red wave" election.[1]
Republicans won a net gain of nine Senate seats, the largest Senate gain for either party since the 1980 United States elections. In the House, Republicans won a net gain of thirteen seats, giving them their largest majority since the 1928 elections. In state elections, Republicans won a net gain of two gubernatorial seats and flipped control of ten legislative chambers. Various other state, territorial, and local elections and referendums were held throughout the year. https://en.wikipedia.org/wiki/2014_United_States_elections