The two leading contenders for the Democratic presidential nomination will return to the Senate today to help determine the fate of a series of high-profile gun measures, marking the first time this session either has cast a floor vote.

Sens. John Edwards (D-N.C.) and John Kerry (D-Mass.) will spend part of Super Tuesday in the Senate chamber voting on at least two issues identified as critical to Democratic voters. The votes, to extend a ban on assault weapons and close the so-called “gun show loophole,” are expected to be so close that Vice President Cheney is also likely to be present to cast the deciding vote if needed.

“Clearly having the vice president there to break the tie sends a clear message to Democrats that we mean business,” said a GOP leadership aide. In his role as vice president, Cheney also serves as the President of the Senate.

Cheney’s presence will set up an odd dynamic in which the two Senators will be facing off against one of the men they hope to put out of work in November. The vast majority of Senate Democrats and a handful of Republicans hope to pass an extension of the assault weapons ban and legislation to prevent individuals from purchasing firearms at gun shows without first being subjected to a background check.

“Senator Kerry is committed to returning for votes where his vote can make the difference on the outcome of the vote,” said Michael Meehan, a senior Kerry political adviser. “It became clear on the military assault ban vote and other gun safety votes the margins were very narrow and Senator Kerry wanted to be here to vote on these important issues that split the Senate.”

Mike Briggs, Edwards’ Senate spokesman, echoed Meehan’s comments, saying the North Carolina Democrat planned to return to the Senate by mid-morning.

As of Monday night, Kerry was slated to take to the floor to make a speech on the gun-control issue before the vote took place and will stay in Washington to monitor returns from the 10 Super Tuesday states tonight. Edwards was still working out his schedule, and it is unclear if he too will take the Senate floor to speak on the issue.

Still, the Kerry-Edwards contest could be over as early as Wednesday if the Massachusetts Democrat sweeps the 10 states, which include Georgia, a Southern anchor seen as critical to the North Carolinian’s claims of electability in that region of the country. Edwards has also invested significant time and money in trying to win in Ohio.

Even though these two Senators have been trading increasingly pointed barbs in recent weeks as the race has winnowed down to a two-man affair, Democrats are gleeful that they are returning to the Senate to display a united front.

“This is a demonstration of how important the assault weapons ban and closing the gun-show loophole are to all Americans,” said a top Democratic aide. “How ironic it will be to have Kerry and Edwards in the chamber to pass an extension of the assault weapons ban and the gun-show loophole and Cheney in the chamber to try and kill” the bills.