Days after lawmakers sidelined a proposed assault weapons ban, Vice President Joe Biden and New York City Mayor Michael Bloomberg on Thursday offered a stern warning to Congress: there are still political consequences for opposing the measure.

"Even though restrictions on military-style weapons will not be part of the bill that goes to the floor of the U.S. Senate, it will get a vote by the full Senate as an amendment to the bill. And everyone’s going to have to stand up and say yea or nay, and then the rest of us have to decide just how we feel about people and their stands," Bloomberg said at a New York press conference with Biden and several family members of children killed in last year’s Sandy Hook Elementary shooting.

Bloomberg urged members of the public to tell congressional opponents of the gun control measure that they will “support whoever runs against you, no matter who they are.”

New York City Mayor Michael Bloomberg speaks about gun reform on Thursday at an event with families that have suffered loss due to gun violence.

"Congress just has to get some courage and it's up to us as Americans and as fellow human beings to give them that courage," he said.

For the billionaire mayor, that “courage” also means “cash.”

Bloomberg has already put millions behind his efforts to elect lawmakers who support gun control -- and his aides say he plans to use millions more on ads to sway those who might vote against it.

Biden, in New York to meet with Bloomberg just days after the Senate dropped the assault weapons ban from its gun bill, insisted that public opinion has shifted on gun restrictions -- and that the political pressure from the gun lobby has been overstated.

"It must be awful, being in public office and concluding that even though you might believe you should take action that you can't take action because of the political consequence you face. What a heck of a way to make a living. What a heck of a way to have to, have to act," Biden said. "The message I want to get across, Mr. Mayor, is the risk does not exist as is exaggerated today."

A suite of new gun control restrictions is winding through Congress, with Senate Democrats set to outline a package that could include new school safety measures, universal background checks for gun buyers and tougher penalties for straw purchasing and gun trafficking.

But it's already clear that the politics of gun control are still difficult -- and as the Newtown massacre fades into the national memory, it's only going to get harder. Senate Majority Leader Harry Reid this week informed California Sen. Dianne Feinstein that the assault weapons ban she's championed for decades won't be included in the bill, all but dooming its chances.

Senators will still vote on the ban as an amendment to the bill, allowing advocates the chance to see who voted against it and giving red state Democrats the chance to show they're opposing Obama's gun restrictions. There will be a second, separate vote on an amendment to ban high-capacity magazines.

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