In the year of the supposed angry electorate, millions of frustrated voters have put their weight behind the outsider presidential campaigns of Donald Trump and Bernie Sanders but continue to back congressional incumbents -- ousting only one so far in hundreds of 2016 primaries contests.

The lone victim was Pennsylvania Democratic Rep. Chaka Fattah, but his ouster appeared more about questionable ethics than frustration with Washington insiders. The 11-term congressman is facing a 29-count federal indictment related to racketeering, bribery and mail fraud.

“The year of the outside candidate is a neat, tidy package put out by the media to a certain extent,” David Payne, a Republican strategist and partner at Vox Global, said this week. “But it’s only part of the story. Look at all of the insiders who are picking up 60 percent of the vote.”

Payne argues that House districts have been “so carefully constructed” by state party officials and others to “remain stable” that few primary races are now competitive.

To be sure, members of Congress rarely lose a primary race, in which incumbents (typically) face a challenge from candidates in their own political party.

Over the past three election cycles, just 17 congressional incumbents have been ousted in a primary -- four House members in 2014, five House members and one senator in 2012, and four House members and three senators in the so-called 2010 Tea Party revolution.

With claims to as many as seven upsets in the 2010 primaries, the conservative, grass-roots Tea Party movement will likely have more success than the 2016 electorate in ousting incumbents.

The 2010 defeat of three-term Utah GOP Sen. Bob Bennet, a reliable conservative, by Tea Party-backed Mike Lee indeed rattled the political class.

But the race that now seems to stick with voters and others is the 2014 upset of House Majority Leader Rep. Eric Cantor. The Virginia Republican and member of House leadership was stunningly upset that year by Dave Brat, a first-time candidate with Tea Party support.

The post-script to the race suggests Cantor paid too little attention to his district.

But beyond getting ousted over so-called “ideological purity,” Capitol Hill lawmakers also often lose primaries amid an ethics scandal, as a result of redistricting (include eight in 2012), or are “accidental candidates” who get elected when, for example, their party’s top candidate unexpectedly drops out.

This year, Trump, a billionaire businessman and first-time candidate, beat more than a dozen Republican lawmakers or former elected officials to become the party’s presumptive presidential nominee.

And Sanders, a self-describe democratic socialist, has kept his insurgent campaign alive in the Democratic primary by portraying front-runner Hillary Clinton as a Washington and Wall Street insider.

Louis Jacobson -- a columnist for the magazine “Governing” and a senior correspondent for the Tampa Bay Times’ “PolitiFact” -- suggested Friday that if the angry electorate indeed exists, only “big personalities” on the national stage appear capable of getting voters riled and into polling stations.

“I’m not seeing a whole lot of it” in gubernatorial and other state-level races, Jacobson said.

He argued that congressional districts have become so blue or red over the years that it’s nearly impossible for a challenger to be more conservative or more liberal that a sitting House member. And he suggested that Congress appears “amorphous” among voters, who tend to know more about presidential candidate, which results in more targeted anger.

Such a theory might help explain why Hill lawmakers continue to win 2016 primaries despite have historically low approval ratings.

A recent Gallup survey found just 17 percent of Americans approved of the job Congress is doing. That rating has not exceeded 20 percent since October 2012.

“Voters generally feel (members) aren’t very good,” Jacobsen said.