Obama has met with a series of gun control advocates in recent weeks as his aides complete work on a potential order expected to expand background checks on gun sales by closing the so-called "gun show loophole."
A timeline on the order -- which has been tangled in legal and administrative questions -- is still unknown. The President met with former U.S. Rep. Gabby Giffords, who was gravely wounded during a 2011 shooting in Tucson, Arizona, on December 4 to discuss gun control.
But even as he works to tighten access to firearms, a new survey shows dwindling support for an outright ban on assault weapons, which both Obama and Bloomberg have advocated as a means to prevent gun deaths.
The White House said Wednesday evening that Obama and Bloomberg "discussed ways to keep guns out of the hands of those who should not have access to them and what more could be done at the state and local level to help address gun violence in America."
As leader of the nation's largest city, Bloomberg was a vocal advocate for tighter gun laws, launching Mayors Against Illegal Guns in 2006 with then-Boston Mayor Tom Menino.
In the aftermath of the 2012 Sandy Hook elementary school massacre in Connecticut, the group morphed into Everytown for Gun Safety, which pushed for new laws in cities and states across the country. Bloomberg poured millions of his own fortune into the group, which helped fund campaigns of pro-gun control candidates.
The organization was meant as a counter to the NRA, whose ratings play a large role in some contests around the country, and whose funding has helped propel pro-gun candidates into office.
Bloomberg's group had a mixed record in supporting candidates in the 2014 midterm elections, but the former mayor has nonetheless pledged to spend millions backing down-ballot candidates in 2016.
That has earned Bloomberg the scorn of the NRA and other gun control groups, who have painted him as a national poster-child for restricting access to guns.
The group spent $1 million in August to run ads around the first Republican presidential primary debate characterizing Bloomberg as intent on restricting Constitutional freedoms.
During Tuesday's CNN debate in Las Vegas, the NRA debuted a Snapchat filter allowing users to display the words "Hey Bloomberg, don't NYC my Nevada gun rights" on their photos.
Revived gun debate
The gun control debate -- which escalated after the Newtown shootings but quieted in the years afterward -- has been revived on a smaller scale by recent shooting tragedies.
After an October rampage at an Oregon community college, Obama tasked his aides with reviewing current gun laws for openings where he could take executive action.
Officials say expanding background checks by closing the "gun show loophole" is the most likely option, though they concede legal and administration hurdles have slowed the process.
Gun control advocates have long pushed lawmakers to require background checks on all gun sales. While some vendors at gun shows are currently mandated to complete background checks before sales, others are considered private dealers or only "occasional" sellers and thus not obliged by law to submit the buyer's name for checking.
What could Obama do?
In his executive action, Obama could alter the government's definition of who is "in the business" of selling guns, expanding it to include private dealers and others who can currently sell without completing a background check. Democratic Presidential candidate Hillary Clinton has already said she would take such action if elected to the White House.
But the legal hurdles in moving unilaterally have proven difficult for the administration to surmount. If he does move forward with executive actions, they would almost certainly be challenged in court by Republicans and groups like the NRA.
And like previous executive actions, Obama's move on guns could be overturned by his successor.
Valerie Jarrett, Obama's senior adviser who also attended the meeting with Bloomberg Wednesday, said this week that the executive orders would be revealed in "short order," but refused to offer any more detailed timelines.
Sliding support for assault weapon ban
Despite Obama's efforts, and Bloomberg's millions, used to advance new restrictions on accessing guns, a new survey Thursday showed support for a ban on assault weapons sliding.
The Washington Post/ABC News survey
showed 45% of respondents backing a ban on assault weapons like the AR-15, a military-style rifle used in a number of mass shootings, including in Aurora, Colorado, Newtown, and San Bernardino.
That's down from 2013, when more than 50% of Americans backed a ban on assault weapons. And it's a sharp decline in support from decades ago, when a vast majority of Americans -- as high as 80% -- supported such a law.
For the first time, the poll showed a majority of Americans, 53%, opposing an assault weapons ban. And a plurality, 47%, now say that allowing more people to carry guns legally is a more effective way to combat terrorism than enacting stricter gun control laws.