Democrats would appear to face long odds in the 2018 U.S. House elections. They need to pick up 24 seats to take back control of the House, and there are only 23 Republicans who hold districts carried by Hillary Clinton in 2016. In this politically-polarized era, presidential election results strongly predict House election results, and Democrats also have to defend 12 of their own seats in districts carried by Donald Trump.
But in 2006, the last midterm election with a Republican in the White House, Democrats appeared to face even longer odds. At that time, there were only 18 Republican seats in districts carried by John Kerry in 2004, and Democrats had to defend 42 of their own seats in districts carried by George W. Bush. Nevertheless, Democrats were able to win back control of the House, making a net gain of 31 seats. In addition to winning 10 of the 18 Republican seats in districts carried by Kerry in 2004, Democrats won 20 Republican seats in districts carried by Bush and won an open seat previously held by then-Rep. Bernie Sanders (I-VT).
The lesson of 2006 for Democratic strategists is not to focus exclusively on districts carried by Hillary Clinton but to cast their net considerably wider. In a midterm election with an unpopular president, the out-party can win a considerable number of seats in districts carried by the president’s party in the previous election. In 2006, Democrats took back 10 of 41 Republican seats in districts in which George W. Bush won between 50% and 55% of the major-party vote and seven of 58 districts in which Bush won between 55% and 60%. They even captured three districts in which Bush won at least 60% of the vote.
Just before Election Day in 2006, George W. Bush had an approval rating in the Gallup Poll of 38%. According to Gallup as of Wednesday afternoon, President Donald Trump’s approval rating stood at 42%, which is historically low for a new president. His approval rating in a recent Pew Research Center poll was even a little lower (39%), though other surveys show more mixed numbers for the president. If Trump’s approval rating remains at this level or declines further, Democrats could have a good many opportunities to pick up Republican House seats in 2018.
In addition to 23 Republican seats in districts carried by Hillary Clinton, there are currently 32 Republican seats in districts that Donald Trump carried with less than 55% of the major-party vote, and 63 Republican seats in districts that Trump carried with between 55% and 60%. Based on the results of the 2006 midterm election, the combination of an unpopular Republican president and strong Democratic challengers could put enough of those seats in play to allow Democrats to win back control of the House of Representatives.