Washington (CNN) Two of the most complex issues in American politics -- gun control and gerrymandering -- are colliding this week in Washington.

The Sunday night shooting in Las Vegas that left 59 dead and hundreds more injured has restarted a debate over whether Congress should impose stricter gun laws, particularly around background checks for gun buyers and the sale of semi-automatic firearms.

But Democrats pushing for those laws have run into the same roadblocks that stymied former President Barack Obama in the wake of the Sandy Hook Elementary shooting in 2012: The National Rifle Association's overwhelming influence in Republican strongholds.

That power comes largely as a result of the extreme partisan makeup of most of the nation's congressional districts: The primary is a more serious threat to most incumbents than the general election. And in Republican primaries, the NRA's endorsement and advertising dollars carry huge weight.

"It gives the NRA leadership an enormous outsized influence on these members," said Jason Kander, an Army National Guard veteran and the former Democratic Missouri secretary of state. "They're more afraid of losing a primary than they are more people losing their lives."

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