Editor's note: This story has been updated to include information on how U.S. Sen. Ted Cruz voted Monday.

A week after the deadliest mass shooting in the country's modern history, the U.S. Senate on Monday voted down four competing gun control measures largely along party lines, including one put forward by Texas Republican Sen. John Cornyn that sought to block the sales of weapons to people on the FBI’s terrorist watch list.

Under Cornyn’s bill, the attorney general would be given 72 hours to prove there was a probable cause for denying a suspected terrorist the ability to purchase a gun. The measure garnered support from the National Rifle Association but failed on a 53-47 vote. It needed 60 votes to pass.

“We all agree that terrorists should not be able to purchase a weapon; that is not up for debate,” Cornyn said before the vote. “The question before us is whether we're going to do so in a way that's constitutional.”

U.S. Sen. Ted Cruz, R-Texas, who has a fractious relationship with Cornyn, voted in support of his colleague's bill.

At a Senate hearing last week, Cruz knocked Democrats for politicizing the Orlando mass shooting and said it has less to do with gun control than the nation's approach to defeating ISIS —a terrorist group the shooter pledged allegiance to.

Cornyn and U.S. Sen. Dianne Feinstein, D-California, have attempted to find common ground on legislation to prevent suspected terrorists from buying firearms. But they ended up with vastly different proposals. Feinstein’s measure, the Democrats’ alternative version, failed by a 47-53 vote. It would have allowed the attorney general to ban the sale of guns to known or suspected terrorists if there was "reasonable belief" the weapons may be used to carry out an attack.

But Cornyn, the Senate's majority whip and second-highest ranking member, said Feinstein’s measure would violate the Second Amendment by denying due process to those on the watch list.

“My amendment is called the Shield Act, and it would stop terrorists from buying guns while ensuring law-abiding citizens placed on a watch list by mistake don't have their rights taken away because of some secret list created by the Obama administration or by this government,” he added.

Feinstein disagreed and questioned the feasibility of Cornyn’s bill, saying that it's “nearly impossible” to mandate the Department of Justice provide evidence within 72 hours. She said the FBI’s database is “clearly vetted.”

Still, left-leaning groups, including the American Civil Liberties Union, had long complained about the credibility of the FBI database and argued that individuals such as former Sen. Ted Kennedy, D-Massachusetts, were inadvertently added to the watch list. The ACLU also said the database is “unconstitutionally vague, and innocent people are blacklisted without a fair process to correct government error.”

The reluctance by lawmakers to pass gun legislation came a week after the Orlando nightclub massacre where 49 people were killed and 53 injured. Democratic senators waged a nearly 15-hour-long filibuster demanding congressional action. Monday's votes underscored the deep partisan divide over gun control, which has long prevented new federal regulations on gun purchases despite the recent rash of mass shootings across the country.

“ We all agree that terrorists should not be able to purchase a weapon, that is not up for debate. The question before us is whether we're going to do so in a way that's constitutional. ” — U.S. Sen. John Cornyn

Democrats say a federal law prohibiting the sales of guns to suspected terrorists would have prevented Orlando shooter Omar Mateen from legally buying the weapons he used because the FBI had investigated him earlier for possible connections to terrorism.

Mateen was investigated by the FBI in 2013 and 2014, but no credible threat was ever found, according to agency officials. He was not under investigation at the time of the attack. Mateen pledged allegiance to the Islamic State in a 911 call during the rampage, authorities said last week.

The Senate also defeated 53-47 a proposal from Sen. Chuck Grassley, R-Iowa, seeking to reauthorize funding for the National Criminal Instant Background Check System and incentivize states to share mental health records with the federal system. It also called for the commission of a study on the causes of mass shootings.

The other competing measure, proposed by Sen. Chris Murphy, D-Connecticut, failed 44-56. It would have expanded the background check system for online and gun show sales. The proposed bill required federal agencies to identify individuals prohibited from buying a gun and imposed penalties on states that fail to make its date electronically available to the background check system.