"This week, the U.S. Senate is getting ready to vote on a bill that would go a long way toward preventing gun violence and making our communities safer.That's because, in the wake of tragedies like the shooting in Newtown, Connecticut, people like you spoke out to demand action from Congress," the email says. "We cannot let up on our senators — not when we've come this far. This Tuesday, April 16th, we're holding a National Call Day to make sure the voices of ordinary Americans are heard in this debate."

The next few days will be pivotal in the gun control debate. The Manchin-Toomey proposal is expected to come to a vote on Wednesday, representing gun-control advocates' best hope at expanding background checks. The moment also presents a key test for the pro-Obama group, which has sought to influence policy in the wake of the election.