Sen. Michael Bennet told CBS News the Senate should pass the gun control legislation the House approved in February, which mandates federal criminal background checks on all gun sales.

Former Vice President Joe Biden headed the gun task force that led the Obama administration to push for legislation requiring universal background checks in 2013. Biden has tweeted that "it’s clear we need to ... close the loophole that allows individuals to buy guns online or at gun shows without a background check."

Former Mayor Michael Bloomberg has called for creating a background check system to ensure that "no one can purchase a gun without passing a completed background check."

Sen. Cory Booker calls for “universal background checks” to close the “gun show loophole” and the “Charleston loophole.”

Gov. Steve Bullock announced his support for "universal background checks and cracking down on straw purchases of guns" in an op-ed in The Great Falls Tribune.

Former Mayor Pete Buttigieg calls for “universal background checks.”

Former Housing and Urban Development Secretary Julián Castro said during a CNN town hall that "we need to make background checks universal."

Mayor Bill de Blasio suggested he supported universal background checks in an interview with POLITICO.

Former Rep. John Delaney calls for “universal background checks on gun sales, including closing the loophole for private sellers.”

Rep. Tulsi Gabbard has called on Congress to pass legislation instituting "universal background checks" and "closing the gun show loophole." She was a co-sponsor of the background checks bill the House approved in February.

Sen. Kirsten Gillibrand called for “universal background checks,” as well as closing “gun sale loopholes.”

Sen. Kamala Harris calls for “universal background checks,” as well as prohibiting those convicted of a federal hate crime from buying guns.

Former Gov. John Hickenlooper called for "a national system of universal background checks to address the state-by-state patchwork and loopholes." He also proposed closing the "Charleston loophole" by expanding the gun background check waiting period to 10 days.

Gov. Jay Inslee has sought to further strengthen background checks in Washington since the state's voters passed an initiative in 2014 requiring background checks for all gun sales and transfers.

Sen. Amy Klobuchar calls for “universal background checks by closing the gun show loophole.”

Mayor Wayne Messam told the Independent Journal Review he "would push for universal background checks" as president "for the purpose of just ensuring any individuals who should not have a gun, not have one."

Rep. Seth Moulton was a co-sponsor of the background checks bill the House approved in February and has called for the Senate to take up the measure.

Former Rep. Beto O'Rourke called for "universal background checks without exceptions" in an op-ed in The Houston Chronicle.

Rep. Tim Ryan was a co-sponsor of the background checks bill the House approved in February and has called for the Senate to take up the measure.

Former Gov. Deval Patrick signed a comprehensive gun reform bill into law in Massachusetts in 2014. The legislation expanded background check requirements to include private firearm sales.

Sen. Bernie Sanders calls for “expand[ing] background checks," closing the “gun show loophole" and making all gun purchases “subject to the same background check standards.”

Former Rep. Joseph Sestak calls for closing the “gun show loophole” and "creating a more effective national background check system, including by enabling states to add felons, domestic abusers, and other violent criminals to the background check database."

Billionaire activist Thomas Steyer has called for a national referendum to institute universal background checks via popular vote.

Rep. Eric Swalwell called for implementing “background checks for all firearm and ammunition purchases, regardless of whether the seller is federally licensed, a gun show vendor, or a private seller;” called for requiring “all background checks to include a search of the National Data Exchange’s 400 million records;” and called for instituting a “system that automatically notifies state law enforcement when someone who is prohibited from purchasing a firearm attempts to do so and is flagged during a background check.”

Sen. Elizabeth Warren said during a CNN town hall that "we need universal background checks."

Author Marianne Williamson calls for “required universal background checks, including at gun shows.”

Entrepreneur Andrew Yang calls for requiring all gun owners to "pass a federal background check, eliminating the gun show loophole."