WASHINGTON — As the student-led March for Our Lives movement captured the nation’s attention in the weeks after the Parkland shooting, the other side of the gun control debate enjoyed a banner month of its own. The National Rifle Association’s Political Victory Fund raised $2.4 million from March 1 to March 31, the group’s first full month of political fundraising since the nation’s deadliest high school shooting on Valentine’s Day, according to filings submitted to the Federal Election Commission.