Washington - Most Americans favour tougher gun control laws as they repeatedly endure the tragedy of school shootings, one massacre after another, and other random gun violence. So why doesn't Congress do something?The paradox enrages gun control activists, who accuse lawmakers of inertia and hypocrisy.But this seeming no-brainer is not limited to gun violence, and it stems from many, many decades of how Americans do politics.Imperfect representation With the way Congressional districts are carved up, and a two-chamber system in which the Senate holds as much weight as the House of Representatives, Congress is far from being an exact representation of the US population.Winning a majority of the votes does not necessarily mean you achieve a majority in Congress. And this is even more true for the office of president, which is elected indirectly, through the Electoral College.READ: Heartbroken by gun violence: Rallies across US demand change"The founders intended the system to work in a way that would guard against policy changing with the whims and passions of the citizenry," Gregory Wawro, a political science professor at Columbia University, told AFP."But that comes at a cost of making it difficult to change policy, even when there is significant demand for it," he added.What's a majority, anyway? On any given issue, there are different kinds of majorities.Take the issue of immigration: polls show that Americans back the idea of "secure borders" - but they don't want a wall built along the frontier with Mexico, as President Donald Trump plans to do.Americans want to see young undocumented immigrants who came to the country as kids get some kind of legal status, but they also want to cut the number of legal immigrants who are coming in now.Democrats and Republicans alike say they represent the majority, and struggle to reach a legislative compromise that reconciles all these competing demands, which are sometimes contradictory.Martin Luther King jnr's granddaughter appeals for 'gun-free world'The 9-year-old granddaughter of Martin Luther King jnr made a rousing appearance at a huge protest for gun control in Washington on Saturday, saying that like the slain civil rights leader she too has a dream - "a gun-free world".On the issue of guns, 97% of Americans favor universal background checks on people wishing to buy a firearm, according to a Quinnipiac survey.But that percentage goes down depending when other gun control measures are put up for debate: 83% back a waiting period after a gun purchase, and 67% favour banning assault-style rifles like those often used in mass shootings.When lawmakers try to calibrate any kind of reform package, they hit a wall.Not a priority for CongressSupporting a policy does not mean voters make it a top priority when they go to the polls."Elections are very imperfect mechanisms for holding elected people accountable," said Jennifer Nicoll Victor, a professor of political science at George Mason University.Voters often have only two ways to answer a bunch of different questions - when you factor in their mood on Election Day, and what is churning through the rapid-fire news cycle at that moment, results may not accurately reflect voters' beliefs.This probably explains why, for instance, many Americans remain loyal to Trump while not believing him when he denies having had relationships with porn star Stormy Daniels, Playboy models and other women who say they had extra-marital sex with him. They feel this scandals are not enough to dump Trump altogether.Behold the mighty lobbyists As far as firearms go, the National Rifle Association plays a pivotal role in how the debate has become so intractable.The NRA is not just a powerful lobbying organization, says Nicoll Victor. Rather, it has "built a culture of gun interests and gun rights and gun manufacturers and gun enthusiasts."Republicans in Congress are part of this culture and balk at the idea of questioning it, even slightly, out of fear of being cut off from the group and its deep pockets when it comes to campaign contributions.But the anti-gun movement has been slower to build a major grassroots wave.Massacres at Columbine High School in Colorado in 1999 and Sandy Hook Elementary School in Connecticut in 2012 gave rise to activist organizations.But it was not until the Valentine's Day massacre at the school in Parkland, Florida that the gun control movement really started to gain momentum, with hundreds of thousands of students and others protesting in Washington last weekend.Polarized political parties In 1986, then president Ronald Reagan, a Republican, signed a bill granting legal status to 2.7 million undocumented immigrants. In 1996, Democrat Bill Clinton enacted a law making it harder for poor people to access welfare benefits.In both cases, the president had to cross the political aisle: Reagan dealt with a House controlled by the Democrats, and Clinton reached agreement with a Republican majority on Capitol Hill.John Hudak, a senior fellow at the Brookings Institution in Washington, recalls also that many Republican lawmakers backed a ban on assault rifles in 1994. That measure expired in 2004."This was a time when gun control was a less partisan issue," Hudak said."You could never imagine a Republican member of Congress, no matter a president, being supportive of something like that today," he added.That's because the two parties have each become more ideologically uniform, and the gap between them is wider than ever.But it is at least conceivable that Trump might be more amenable to reform if the Democrats retake Congress in November's midterm elections.