We've learned when the dormant push for federal action on new gun legislation is to receive its wake-up call: it is "almost certain" to happen sometime in 2014, according to a spokesperson for Senate Majority Leader Harry Reid. Why Reid would want the effort subject to reelection politics is unclear. Pushing immigration reform to 2014, however, might actually make some sense.

Consider what happened to the gun package in the first place. Championed by the president in the aftermath of the Newtown, Connecticut shootings last December, Senate Democrats pushed for new background check requirements, increases in penalties for trafficking weapons, and more money for school security. The effort quickly slammed into a wall of Republican resistance. A measure that would have banned certain types of weapons and magazines, championed by Senator Dianne Feinstein of California, was the first victim. Senator Chuck Schumer's effort to expand background checks was rejected out-of-hand, prompting a compromise from Senators Joe Manchin and Pat Toomey. When that compromise was filibustered in April, Reid tabled the whole thing. Until, apparently, next year.

The compromise, which would have made the entire package viable had Reid found six more votes to break the filibuster, hinged on a few senators. Democrats Max Baucus of Montana, Mark Begich of Alaska, Heidi Heitkamp of North Dakota, and Mark Pryor of Arkansas opposed the effort. Baucus is retiring after 2014, so it's possible he might change his vote with nothing to lose. But he probably won't: When asked why he voted against the measure, he responded, "Montana."

Of the other three, two — Begich and Pryor — are up for reelection and will likely face tough races. (A recent poll from a government employees' union has Pryor up, so far.) Neither faces any primary challenger yet, in case Reid was hoping they might move left to stay on the Democratic ticket. And it gets worse for Reid as November approaches. Other wavering senators who ended up backing the effort face tough races of their own. Like Mary Landrieu of Lousiana. She and Pryor have the two most difficult races for Democratic incumbents next year. North Carolina's Kay Hagan, who also supported the compromise, faces only a slightly easier race. Whether or not either of them will be willing to take another tough vote in light of that is a risky move.

Contrast that with immigration reform. Over the weekend, House Majority Leader Eric Cantor insisted that the House would consider a reform bill "at some point" during the fall. But that bill will not be the Senate legislation, meaning that a compromise between the two chambers could easily last past the new year. If it does, into the timeframe after members of the House have faced primary challenges and are beginning the general election, it could mean passage of a final bill that's closer to the Senate version. A version of the bill, that is, that is less likely to be tied to the more extreme positions of conservative House members.

The Huffington Post made this point last month.

If conference committee negotiators take several months to merge the small House bill with the comprehensive Senate bill, the House wouldn't be asked to vote on it again until next spring or summer -- by which point it will be too late for challengers to launch primary campaigns. …

"There is a significant chunk of House Republicans that want to see something done on this, and the only thing that's holding them back is the fear of a primary challenger," [Lanae Erickson Hatalsky, politics director for Third Way] said. "So the closer we get to these dates and the less likely that primary challenger is to pop up unannounced, the easier it is for them to have their shackles off and do what they really think they should do for the party and for themselves."

The difference is the voters. Immigration has a pool of affected voters that gun legislation does not. There is political value in making a route to citizenship available that doesn't exist with increasing background check requirements. This is, after all, why immigration reform is on the agenda at all: because of the Republican Party's ongoing weakness with Latino voters in general elections.

When President Obama called the rejection of the Manchin-Toomey compromise a "shameful day" in Washington, he demanded that those who shared his opinion contact elected officials to let them know that they disagreed with efforts to block new legislation. Perhaps Reid is hoping that those voters will do so again next year, as Pryor and Begich and Landrieu get ready for election day.

That's a risky bet.