President Obama made an emotional appeal today for members of Congress to put aside political concerns when it comes to gun control and instead vote their consciences, a rhetorical approach that presages his closing argument on the matter with the Senate set to begin consideration of the legislation in early April.

"Shame on us if we've forgotten" Newtown, said Obama. "I haven't forgotten those kids. Shame on us if we've forgotten."  Later, he added: "We need everybody to remember how we felt 100 days ago and make sure that what we said at that time wasn't just a bunch of platitudes, that we meant it."

Just in case you missed the shame/guilt theme, Obama was surrounded on stage by families affected by gun violence -- including some from Newtown, Conn., where a slaughter of 26 people late last year that thrust the debate over gun control back into the national spotlight. "We have moms on this stage whose children were killed as recently as 35 days ago," Obama said. "I don't think any of us can hear their stories and not think about our own daughters and our own sons and our own grandchildren."

While Obama did touch on the political end of the gun debate -- he noted that expanded background checks are wildly popular with the public -- the core of his case was an emotional one. That focus seems to be a tacit acknowledgment that Newtown changed the political dynamics surrounding guns less than many people thought it might in the immediate aftermath of the tragedy.

Major questions remain about the viability of the Senate gun proposal due in no small part to concerns from Democrats up for re-election in 2014 in conservative states -- Arkansas, North Carolina, Montana among others -- about the political reverberations of voting for it.

But the Obama argument seeks to place moral/emotional concerns above political ones. In essence: Forget the politics, do what's right. (California Rep. Xavier Becerra summed up that argument during an appearance on "Andrea Mitchell Reports" on Thursday; "Suck it up. Be courageous. Do the right thing," he counseled wavering Democratic members.)

Of course, it's far easier to vote your conscience when you don't ever have to worry about facing voters again (Obama) or when you represent a district that is overwhelmingly Democratic (Becerra). It's far harder to do so when you are in a district or state where gun rights are considered part of the cultural fabric. (And, it's also worth noting that a vote of conscience may well be a vote against gun legislation for some of the members.)

Will Obama's approach bend some Democratic senators (and even a few Republicans) to vote for his legislative package on guns? Maybe. But, in our experience, votes of conscience are a luxury that vulnerable incumbents don't believe they have.