With less than a month to go until the Iowa caucuses, the top two Democratic candidates' campaigns are taking pot shots at each other on gun control.

On Friday, John Podesta, the chairman of Hillary Clinton's presidential campaign took aim at her closest threat, Bernie Sanders, highlighting the Vermont senator's murky history with gun control.

In a tweet, Podesta cited a 2005 Senate vote on the Protection of Lawful Commerce in Arms Act, a National Rifle Association-backed bill that protected gun manufacturers from lawsuits when their guns are used in crimes. Then-Sens. Clinton and Barack Obama voted against it. Sanders voted for it.

Podesta's attack attracted the attention of another top Democratic operative, David Axelrod. "Shootout at Ft. Des Moines corral? As caucuses approach, Team @HillaryClinton has @SenSanders within their sights," the former Obama campaign strategist tweeted.

Gun regulation has become a hot button issue after President Obama issued executive orders requiring people engaged in selling guns as a business conduct background checks on all firearm buyers.

Clinton and former Maryland Gov. Martin O'Malley have called for more stringent background checks for gun purchases. Sanders has been less vocal on the issue, though he supports Obama's executive actions.

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