Military veterans voted for Republicans by a 20 percentage-point margin over Democrats in House races last week, according to the national network exit poll. Veterans made up 17 percent of all voters this year, and their strong preference for Republicans should come as no surprise -- Mitt Romney won veterans by 20 points in 2012 according to the American National Election Studies post-election survey (the exit poll did not ask veteran status that year).

Demographics explain part of why veterans have consistently backed Republicans. Almost nine in 10 veterans are men and half are over age 60, both groups that tend to vote Republican.

But even among these groups veterans tilt more Republican than the public at-large. The oldest veterans backed Republicans by 27 points, while non-veterans in the same age group favored Republicans by a 4-point margin. Veteran men backed Republicans by 26 points, compared with a 12-point margin among male non-veterans. Women are an exception to this trend -- exit poll included fewer than 100 women, but they leaned toward Democrats by a slightly wider margin than the public overall.

Veteran voters are not monolithic, and Democrats perform fairly well among those with lower incomes and non-whites, groups where the party also excels among non-veterans. Democrats split veterans with household incomes below $50,000 with Republicans in this year’s House elections, and won non-white veterans by a 64 to 35 percent margin. Both margins were smaller than Democrats’ advantages among lower income and non-white voters generally, providing additional evidence of veterans’ Republican tilt.

Republicans may win an even greater share of the veteran vote in the future. A 2012 Pew Research survey found veterans who had served since the Sept. 11, 2001 terrorist attacks were 15 percentage points more likely to identify as Republicans than Democrats, compared with a four-point GOP edge among pre-9/11 veterans.

These mirrored results in a 2013 Washington Post-Kaiser Family Foundation survey of those who served in the Iraq and Afghanistan wars. By 45 to 33 percent, more said they leaned toward the Republican Party than the Democratic Party.

Peyton M. Craighill contributed to this report.