Why did the expanded background-check proposal fail in the U.S. Senate in 2013?

In April 2013, the U.S. Senate proposal to expand gun-control background checks failed because it did not reach the required filibuster-proof supermajority of 60 votes. Although the measure received a simple majority of 54–46, it fell short of the threshold needed to proceed to a formal vote.1

The failure of the legislation was significantly influenced by the National Rifle Association (NRA) and other gun-rights advocates, who actively campaigned against the bill. While public opinion polls at the time indicated widespread support for universal background checks, the Senate vote largely followed party lines, with a few exceptions from both parties. Following the failure of this measure and several related amendments, the bill was withdrawn.1