With gun control advocates facing off against gun rights groups to push for legislation after Parkland, each side is cementing their messages and setting goalposts for what is - and isn't - up for discussion. (Jenny Starrs/The Washington Post)

President Trump has backed off his call to raise the minimum age for rifle purchases — or at least that’s what Sen. Pat Roberts (R-Kan.) believes.

Sen. Chris Murphy (D-Conn.), meanwhile, thinks the administration is seriously weighing expanding background checks for gun purchases. Yet Senate Majority Whip John Cornyn (R-Tex.), a close ally of the White House who has spoken with Trump about the issue, has personally gotten no such indication.

Lawmakers, in other words, have no real idea what Trump wants from them on gun policy in the wake of the massacre at a South Florida high school.

“It’s really unclear what they’re for and what they’re not for,” Murphy, one of the most prominent gun-control advocates on Capitol Hill, said Tuesday. “I don’t think there’s a secret agenda that they have not released. I think it’s just hard. I think they’re trying to figure it out.”

In advance of a bipartisan gun summit at the White House on Wednesday, lawmakers are searching for signals from the administration on how it wants Congress to respond to the Feb. 14 shooting and how serious Trump is about the various proposals he has floated in the days since 17 people were gunned down at Marjory Stoneman Douglas High School in Parkland, Fla.

President Trump pauses as he listens to people recount stories of the school shooting in South Florida during a listening session with high school students and teachers at The White House on Feb. 21. (Ricky Carioti/The Washington Post)

There is also an open question in Congress about how much Trump will actually affect the debate, with some Senate leaders pushing for more guidance from the president, given his continuing focus on the shooting, while other top senators are skeptical that any guidance from the mercurial president — such as during the stalemate on immigration — will ultimately matter much.

Trump and his senior aides have publicly floated several gun-related proposals since the shooting in Parkland, including legislation to encourage agencies to report relevant information to a federal database used to screen potential gun buyers, banning devices known as “bump stocks” and arming teachers, a controversial proposal Trump has emphasized in his public remarks.

Trump has also discussed raising the minimum age for rifle purchases to 21, despite opposition from the National Rifle Association — a policy White House press secretary Sarah Huckabee Sanders said Tuesday that the president still supports for “certain firearms.”

The White House has invited an assortment of lawmakers to Wednesday’s meeting, including Murphy; Cornyn; Sen. Joe Manchin III (D-W.Va.), who co-authored a universal background check measure in 2013; and Sen. Dianne Feinstein (Calif.), the top Democrat on the Judiciary Committee, who wrote the 1994 assault weapons ban.

Sanders said the administration plans to release some policy proposals this week, probably giving some clarity to the GOP-led Congress on where Trump wants to focus and whether there will be any areas of tension between the White House and congressional Republicans — particularly the most conservative lawmakers.

“The president, as you know, has made a number of statements over the past few days,” said Sen. John Thune (S.D.), the third-ranking Senate Republican. “Him weighing in probably matters quite a bit with a lot of members, and, you know, what he would like to see done. But the Congress is going to work its will on this, like it usually does.”

Rep. Chris Collins (R-N.Y.), a close Trump ally, said lawmakers want Trump to take the lead on the gun debate.

Frustration is boiling over on both ends of the political spectrum at the inability to stop mass shootings, but many still can't agree on a path forward. (Jenny Starrs/The Washington Post)

“I don’t think there’s any consensus whatsoever that there’s anything on, quote, gun control,” Collins said. “We’re an independent body, and we will do what our members think is best.” But, he added, “I would say the president’s leadership on this is going to be key; there’s no doubt.”

Republican leaders have been hesitant to weigh in publicly on how to respond to the Parkland shooting until they know where Trump stands and what policies could be supported by their members.

On Tuesday, neither Speaker Paul D. Ryan (R-Wis.) nor other House GOP leaders would commit to holding a vote on modest gun-related measures that have broad bipartisan support. Senate Majority Leader Mitch McConnell (R-Ky.) wants to pass the Fix NICS Act, meant to improve reporting to the National Instant Criminal Background Check System. He also began promoting a separate proposal from Sen. Orrin G. Hatch (R-Utah) that would provide grants to states for school safety programs, including training to identify threats and improving physical security through such things as better locks on classroom doors.

The House passed a version of the Fix NICS measure in December, in conjunction with a controversial provision that would force states to recognize concealed-carry licenses from other states. The Senate is exploring passing the background check proposal as a stand-alone measure as soon as this week, but Ryan would not say Tuesday whether he would bring that bill or a ban on bump stocks — devices that allow a semiautomatic rifle to mimic the rapid fire of an automatic weapon — up for a vote.

“We’re waiting to see what the Senate can do,” he said, adding, “We obviously think the Senate should take our whole bill, but if the Senate cannot do that, then we’ll discuss and cross that bridge when we get to it.”

Cornyn said that he spoke with Trump over the weekend and that the president has “a lot of ideas,” but that he hasn’t discussed with him any legislation on background checks broader than the Fix NICS Act. Murphy, meanwhile, said he thinks the White House would be willing to go beyond the bare-bones bill for a more expansive background check measure.

“There’s something stirring over there on background checks,” Murphy said. “I just haven’t exactly figured out what it is yet.”

Democrats said that after years on inaction in Congress following mass shootings, they believe there is momentum to do something substantive and that even members from states and districts where restrictions on gun purchases have traditionally been unpopular are feeling emboldened.

“Not every Democrat will run on banning assault weapons, but every Democrat should be running on background checks,” Murphy said. “Background checks is popular in every state and every congressional district, it’s a loser for Republicans everywhere.”

While lawmakers are left waiting for the administration’s policy proposals, they’re doing their own pitching.

Sen. Patrick J. Toomey (R-Pa.), who wrote the doomed background check measure with Manchin five years ago, spoke directly with Trump earlier Tuesday and is urging him to get behind the duo’s legislation to expand background checks to gun shows and online sales. Trump was “listening,” Toomey said simply of the president’s reception of their idea.

Meanwhile, Hatch has discussed his school safety bill with White House officials. “They’re interested,” he said Tuesday.

In coordination with the departments of Education and Health and Human Services, Sen. Lamar Alexander (R-Tenn.) is working on his own proposal to bolster security at schools, such as by encouraging additional school counselors, a spokeswoman said.

The White House has sought in some instances to feel out what types of legislation may be introduced by lawmakers who have spoken publicly about how Washington should respond to the latest school shooting.

After Roberts said last week that he would support increasing the minimum age to purchase certain rifles to 21, the administration contacted him and asked whether he was planning to introduce legislation along those lines, the senator recalled Tuesday.

Roberts said he wasn’t and added, “I think they’ve backed off it now, though.”

But Trump has discussed raising the purchasing age for rifles with Cornyn, according to the Texas Republican, who isn’t eager to support the idea but said he could probably live with it as part of a bigger gun package.

An unpredictable factor in the ongoing debate is the surviving students from Stoneman Douglas, who have taken a visible role in pushing officials to take action and enact new gun restrictions.

Eight of the students took their case to Capitol Hill this week, culminating in a private meeting Tuesday with Ryan. The students were joined in the meetings by Rep. Ted Deutch, the Democrat who represents the district that includes the school. He described a frank meeting in which Ryan acknowledged that some of the more ambitious gun restrictions the students are advocating — such as a ban on military-style semiautomatic rifles and high-capacity magazines — would not pass the Republican Congress.

But, according to Deutch, Ryan said he was interested in quickly bringing consensus legislation to the House floor on issues such as background checks and school security. Deutch is a co-sponsor alongside Rep. John Rutherford (R-Fla.), a former county sheriff, of a school safety bill unveiled Tuesday that would provide federal aid for security and prevention measures.

“Look, I’ve been very clear about what I think needs to happen, but I’ve also been clear that it’s important that we show that we can act and that we can take steps forward,” Deutch said. “This is a bipartisan piece of legislation. If we can’t come together around something that already has bipartisan support, I’m not sure where we can.”

In a statement released after the meeting, Ryan thanked the students for sharing their experiences and said they “had an important discussion about how to keep our kids and our schools safe.”

“We will continue to work to find common ground on solutions that can help prevent the kind of senseless violence these students endured,” he said.

Ed O’Keefe contributed to this report.