Joe Biden Out of Sight, Out of Mind at Democratic Debate

— -- Much of the buzz leading up to the first Democratic debate was about whether Vice President Joe Biden would enter the 2016 race, but to the five Democratic presidential candidates on the debate stage Tuesday night, Biden was out of sight and out of mind.

While the vice president watched the debate from his residence at the Naval Observatory in Washington, D.C., not one of the presidential candidates brought him up by name during the two-and-a-half hour televised debate.

Had Biden announced his run and appeared at the debate, there would have been ample opportunities for him to stand out. Here's a look at some of those topics where Biden could have found himself at odds with the candidates.

RUNNING FOR A THIRD OBAMA TERM?

Each of the presidential candidates on stage argued they wouldn't be running for a third term of President Obama's administration. But would Biden have been able to say the same thing?

It would have been harder for the vice president to distance himself from the Obama White House, especially as he's become a cheerleader of the administration's policies, including the Trans-Pacific Partnership, which is opposed by the other Democratic presidential candidates.

SYRIA NO-FLY ZONE

Biden could have found himself going head-to-head with Hillary Clinton over Syria. While her opponents attacked her plans, Clinton adamantly defended her call for a no-fly zone in Syria, a proposition the president has called "half-baked."

While he has not weighed in on the no-fly zone debate since Clinton announced her support, the vice president likely would have sided with Obama and gone up against Clinton over Syria policy.

CLINTON'S PRIVATE EMAIL SERVER

Biden has been relatively silent on the issue of Clinton's private e-mail server, so the debate would have given him a very public venue to chime in on the ongoing scandal. Would he have sided with Bernie Sanders' fatigue with the "damn e-mails" or would he have honed in on Clinton's mistake?

THE OSAMA BIN LADEN RAID

As she defended her foreign policy decisions, Clinton raised her role in advising the president on the Osama Bin Laden raid -- a decision where she and Biden drastically differed.

"While you're talking about the tough decision that President Obama had to make about Osama bin Laden, where I was one of his few advisers" Clinton noted.

The vice president has said he advised the president against the raid -- something Clinton could have reinforced in the debate had Biden participated.