As Democrats call for gun reform in the wake of the deadliest shooting in modern US history, will Trump offer divisive rhetoric or a willingness to cross the aisle?

Donald Trump faces a test of temperament on Wednesday as he visits Las Vegas, the scene of the deadliest mass shooting in modern US history, with Democrats stepping up political pressure for tighter gun laws.

It has become a grim ritual for American presidents to visit the scenes of mass murder and gun violence, burdened by expectations that they will be dignified, rise above party politics and perform the unifying role of head of state.

But Trump is already notorious for divisive rhetoric at key national moments, including after the racially charged violence in Charlottesville, Virginia, in August. The National Rifle Association was crucial to his election and he was the first sitting president since Ronald Reagan to address its annual conference, where he vowed to defend the second amendment.

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Since the gunman, identified by police as Stephen Paddock, opened fire from his hotel room, killing at least 59 victims and injuring more than 500 at a country music festival on Sunday night, Trump has struck a measured tone. But on the ground in Las Vegas, where he is expected to meet the state governor and city mayor, and possibly visit survivors in hospital, there will be no shortage of opportunities for a jarring remark. On Tuesday, visiting hurricane hit Puerto Rico, he joked: “I hate to tell you, Puerto Rico, but you’ve thrown our budget a little out of whack. But that’s fine because we’ve saved a lot of lives.”

Democrats intend to throw down the gauntlet before Trump’s plane touches down by staging a high-profile event on the front steps of the US Capitol building in Washington. Congressman and civil rights veteran John Lewis and former congresswoman Gabby Giffords, who survived a shooting in 2011, will be among those calling for the immediate passage of legislation to strengthen background checks on gun buyers, as well as creating a bipartisan select committee on gun violence.

Facebook Twitter Pinterest Donald and Melania Trump at the White House for a moment of silence for the victims of Sunday’s mass shootings. Photograph: UPI / Barcroft Images

In a Republican-controlled Congress, Democrats know the odds are against them. But they think they may have an unlikely ally in Trump, whose views on gun control have shifted since he ran for president as a Republican. Past incidents – such as visceral TV images of children killed by poison gas in Syria – suggest that Trump can be swayed by direct appeals to the heart. On Tuesday the president said: “We’ll be talking about gun laws as time goes by.”

In a floor speech, Chuck Schumer, the Senate minority leader, called on Trump to bring together leaders of Congress as a sign to both sides that he is “ready and willing to address this issue of gun safety head-on”.

Activists and even comedians have called on Trump, who ran as an anti-Washington outsider, to act. Late-night TV host Stephen Colbert said: “You do not owe the Republicans anything. You know the Republicans tried to stop you from being president; well screw ’em. You want to make America great again, do something the last two presidents have been unable to do: pass any kind of commonsense gun control legislation that the vast majority of Americans want.”

Democrats are weary from years of political stalemate over gun control. Senator Chris Murphy, from Connecticut, was visibly frustrated on Tuesday when he condemned members’ “utter silence” in response to ever-rising toll of mass shootings and called their inaction “unintentional complicity”.

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“In the minds of these mad men when they see Congress doing absolutely nothing, shooting after shooting – they read that as quiet acceptance of the carnage,” Murphy told reporters on Capitol Hill. “It has to stop.”

Joined by four colleagues, the Democratic senators outlined “a menu” of gun control measures they planned to introduce, including to expand background checks and to restrict people convicted of domestic violence from obtaining a gun. Senator Dianne Feinstein of California also plans to reintroduce a bill that would ban bump stocks and similar devices, which Murphy said he believes could attract bipartisan support.

Senator Bob Casey, a Democrat of Pennsylvania, cited himself as an example of how one incident can change hearts and minds. Before the 2012 massacre of 26 young children and teachers in Newtown, Connecticut, Casey opposed additional gun restrictions. He said he realised then that opposing the slate of gun control measures brought forward that session meant accepting that nothing could change.

Facebook Twitter Pinterest Senate Democrat leader Chuck Schumer called on Trump to signal he is ‘ready and willing to address this issue of gun safety head-on’. Photograph: Edelm/Zuma Wire/Rex/Shutterstock

He said: “I think we have to ask ourselves the same question again. Is there nothing that we can do? No law? Nothing that we can do? … I don’t think that’s acceptable.”

But there has been little sign that the horror of Las Vegas will budge congressional Republicans. The Senate majority leader, Mitch McConnell, dismissed the debate as “premature” and chastised Democrats for raising the issue of gun control so soon after the attack.

“I think it’s particularly inappropriate to politicize an event like this,” McConnell said. “It just happened within the last day and a half. It’s entirely premature to be discussing legislative solutions – if any.”

He added: “We’re in the middle of an investigation. We’ll see what that reveals and at the end of that will be an appropriate time to discuss it. In the meantime, our priority is tax reform.”

Schumer also called on Republicans to drop a bill that would make it easier to purchase a silencer. Republicans postponed a hearing on the bill in June when members were attacked by a gunman during a congressional baseball practice.

“When two mass shootings force you to delay a bill that would make those mass shootings harder to detect and stop, maybe that’s a sign you ought to let go of the bill, once and for all,” Schumer said. On Tuesday, Ryan said the bill was not currently scheduled to come to the floor.

The deeply entrenched partisan divide on gun control are illustrated by two former House colleagues who were both grievously injured in mass shootings.

Play Video 0:40 Donald Trump calls Las Vegas gunman 'demented' - video

Congressman Steve Scalise on Tuesday joined his Republican colleagues for a weekly press conference. It was his first time at the podium since returning to Washington after he was grievously injured in the June shooting. Scalise urged prayer and did not raise the issue of gun control.

In a Fox News interview later on Tuesday, Martha MacCallum asked Scalise if his experience being shot on a baseball diamond had changed his views on the Second Amendment, which guarantees the right of citizens to “bear arms”.

Scalise, a strong supporter of gun rights, replied: “I think it’s fortified it.”

Scalise is one of only a handful of members of Congress who have been injured while serving in office. Another is Giffords, now a prominent advocate for stricter gun control.

Paddock had an arsenal of 23 guns in his suite on the 32nd floor of the Mandalay Bay Hotel. The retiree had no criminal record and his motive remains a mystery as the criminal investigation continues. On Tuesday Sheriff Joseph Lombardo of Clark County said detectives were in contact with 64-year-old Paddock’s girlfriend Marilou Danley, who is in the Philippines and considered “a person of interest”.

Trump has described Paddock as a “very, very sick individual” and said “we’re looking into him very seriously.”