Vice President Joe Biden carries a bag full of food Nov. 21 as he talks with reporters outside Capriotti's Sandwich Shop in Washington, D.C. Biden is seeking to make himself as central as possible to the White House's orbit of influence.

WASHINGTON — When President Barack Obama summoned congressional leaders for an urgent meeting last month, at the height of a fiscal crisis, Joe Biden wasn’t initially mentioned as a participant. The vice president’s staff quickly followed up with reporters, in case any had been wondering: Biden would be there, too.

On another occasion, Biden boasted at a sandwich shop that Delaware’s subs are superior to those in Chicago and Philadelphia. Then, he let the crowd know he couldn’t linger. “The president is waiting,” he announced to the room. “I’m having lunch with him today.”

The two moments are emblematic of a vice president who has sought to make himself as central as possible in the White House sphere of influence, without overstepping the vice president’s role in ways he has said had left a terrible aftertaste from the Bush White House.

It’s a delicate balance that has at times paid off for Biden. Obama has turned to his leadership and judgment at critical junctures in his presidency, validating Biden both publicly and privately.

At other times, it’s meant being relegated to lower-profile tasks or conspicuously absent at key moments, such as during the problem-plagued health overhaul rollout.

Constitutionally, the vice president has only as much power as the president cares to share. But as Obama’s two-term deputy, Biden will see his political fortunes forever linked to the president, whose approval ratings are sagging amid the health care troubles. How the public ultimately perceives Obama’s presidency — and Biden’s role in it — will be critical to Biden if he runs for president again in 2016, as he plans to consider.

When Time magazine asked Biden what he was thankful for this Thanksgiving, Biden said he was grateful to be someone who wakes up in the morning knowing that what he’s about to do really matters.

“I’m thankful for my personal relationship with the president. I guess it’s a funny way to say it, but it is personal,” Biden said, adding Obama “has entrusted me with some significant responsibilities.”

In a departure from some previous vice presidents, his aides say, Biden has never sought out specific assignments from the president. A particular topic is not what’s important to Biden. What matters is being where the action is.

How you get there matters, too. When he first walked through the doors of the White House, Biden was determined to be different from his immediate predecessor. Dick Cheney’s heavy-handed accumulation of power had drilled a “San Andreas fault” through the Bush administration, Biden said.

“I don’t think the measure is whether or not I accrete the vestiges of power. I think it matters whether or not the president listens to me,” Biden said in January 2009.