Democrats and Republicans are lining up behind competing strategies in response to the latest tragic episode of gun violence, leaving the pair of senators who last spearheaded gun control legislation wondering if there will ever be enough bipartisan buy-in to move a bill across the Senate floor.

Sens. Joe Manchin (D-W.Va.) and Pat Toomey (R-Pa.) were the architects of legislation to strengthen background checks and remove loopholes permitting criminal gun sales in the wake of the 2012 shooting at Sandy Hook Elementary in Newtown, Conn.

Now following last week’s deadly college campus shooting in Roseburg, Ore., Congress is once again facing the question of whether it can advance any effort to stem gun violence.

“It’s as relevant today, if not more so, as it was at that time,” Manchin said Thursday at a news conference held by Senate Democrats to highlight their new set of gun control proposals. “We’ve got Republicans – we just need more, that’s what we’re hoping for.”

Neither Manchin nor Toomey has committed to reintroducing their proposal and the furthest either has gone toward a commitment to revive it is Manchin saying Thursday that “I think we intend to do that, hopefully.”

Instead, Democratic Senators on Thursday unveiled a new campaign to build a “groundswell” of support behind three gun control principles — improve background checks, close loopholes and shut down “straw purchasing” and other illegal gun trafficking — as a precursor to filing comprehensive legislation.

“These ideas would make a real difference in stopping gun violence, but they won’t become law without an outcry from the American people,” said Sen. Ron Wyden (D-Ore.).

Senate Democrats would not say when specifically they would deem public support strong enough to introduce legislation, but Sen. Charles E. Schumer (D-N.Y.) said it would likely be later this year or early next year.

“We will know it, and the American people will know it when they hear it,” Schumer said.

Meanwhile, Republican leaders are taking a different approach and are pushing a bill, penned this summer by Senate Majority Whip John Cornyn (R-Texas), that would address some of the mental health concerns associated with incidents of gun violence rather that focus on restrictions on firearms.

“Some of our Democratic colleagues have said that they’re going to introduce some gun control legislation that we all know has been tried before and cannot pass this chamber,” Cornyn said Thursday, arguing that senators need “a broad consensus… and I believe my legislation can do that by addressing the root cause of some of these horrific events.”

While most Democrats support some focus on mental health as part of a larger gun control bill, they are skeptical about Cornyn’s approach.

“You cannot solve the gun violence epidemic without changing our gun laws,” Sen. Chris Murphy (D-Conn.) said. “We should change our mental health system because it’s broken, but that shouldn’t let Republicans off the hook for the broader problem of illegal guns.”

Manchin spoke somewhat positively about Cornyn’s efforts, noting he hoped to potentially incorporate that legislation into a new Manchin-Toomey bill.

“How in the world can we expect as Democrats to have Republicans supporting common-sense procedures that we’re asking for, when a Republican puts a common sense procedure, and us as Democrats not support?” Manchin said. “I’m going to support whatever makes sense.”

Manchin and Toomey both continue to assert that the approach they designed – which secured 54 votes in 2013, just six shy of the number needed to clear a procedural filibuster hurdle – is still the most sensible.

But they are openly worried that the climate for getting momentum behind that bill may be worsening.

“While I welcome the renewed interest of my Senate colleagues in this critical issue, I worry that a partisan and unbalanced approach will receive even less support than the 54-vote majority the Manchin-Toomey amendment received,” Toomey said in a statement.