During the first Democratic debate, the National Rifle Association became a surprise source of tension, with the candidates defending how aggressively they have opposed the group.

Hillary Clinton said that Vermont Sen. Bernie Sanders hasn't been nearly tough enough on gun control, calling for the entire country to stand up against the NRA.

Former Baltimore Mayor and Maryland Gov. Martin O'Malley touted his record of pushing through gun legislation.

Sanders defended himself by explaining that Vermont is a largely rural area where people feel strongly about their guns. He pointed out that he once received a "D-" rating from the NRA.

Sanders added that O'Malley hasn't served as a senator, so he doesn't know how difficult it can be to get legislation passed in Congress.

Watch Chris Stirewalt and Howard Kurtz react in the "Kelly File" clip above.

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