Just the Facts

When It Comes to Control of the House, the Margin Matters

By No Labels
May 2, 2018 | Blog

In November’s election, both parties are fighting for the 218 seats it takes to control the U.S. House. Yet no matter who wins, they are likely to do so with a slim margin.

In the 100-member Senate, one party or the other has often held the chamber by just a handful of seats in recent years. The low margin defines the action in the Senate. In the 435-member House, the margin has not been much larger. Republicans currently hold the chamber by 22 seats, according to the House Press Gallery.

With the House up for grabs this year—there are 67 House lawmakers leaving office—the margin held by the majority is almost certain to shift and that could have an impact on how they run the chamber moving forward.


Why the margin matters

Simply put, a higher margin allows the Speaker and his or her leadership team to operate with more freedom. When the margin is just a few seats, as it was between 1999 and 2003, retirements, resignations or even a death can jeopardize control. Perhaps more importantly, a small margin makes it harder to marshal support for key pieces of legislation. It is easier for a small group of lawmakers to hold up the process in return for concessions on policy.

In the last 20 years, the House has changed hands twice but the margin has never exceeded 10 percent of the chamber. The largest margin was 39 lawmakers in 2009. The smallest was just three lawmakers in 2001. Here’s a chart showing the margin in the last two decades.


Congress Years Democrats Republicans Majority Margin
115th 2017-2019 195 240 Republican 22
114th 2015-2017 188 247 Republican 29
113th 2013-2015 201 234 Republican 16
112th 2011-2013 193 242 Republican 24
111th 2009-2011 257 178 Democratic 39
110th 2007-2009 236 199 Democratic 18
109th 2005-2007 202 231 Republican 13
108th 2003-2005 205 229 Republican 11
107th 2001-2003 212 221 Republican 3
106th 1999-2001 211 223 Republican 5
105th 1997-1999 207 226 Republican 8


Margins can encourage gerrymandering

For many years, the House was not so volatile. Prior to 1994, Democrats enjoyed nearly unbroken control for decades. “The Democratic Party dominated the House; the Republican Party consigned itself to being the permanent minority; and no one in either party thought partisan control of the House could switch hands in any upcoming election,” wrote Richard Pildes, a professor at New York University, in The Washington Post.

But with narrower margins, control of the House is less secure. That creates an incentive for partisans to try to redraw districts for political advantage, which can increase political polarization by making elections less competitive. Of course, there are also strong arguments that the impact of gerrymandering is overstated, and that there are many other factors that cause polarization. Still, Pildes argues that gerrymandering will get worse. As he wrote, “When the stakes are so high that partisan control of the House might hang in the balance, more aggressive partisan efforts to gerrymander will, not surprisingly, flourish.”

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