WASHINGTON (AP) - 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 was at a sandwich shop boasting that Delaware's subs are superior to those in Chicago and Philadelphia. 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 orbit of influence in the White House, 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 give him or her. 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 that 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, a key player on the issues of utmost importance to the administration, the aides said.
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, not long before he was sworn in.
He also said he didn't want to have a portfolio, consigned to low-priority projects that would underutilize his vast experience built up over decades in the Senate crafting laws and building relationships with world leaders. Nor did he want to lead a task force to reinvent government, Biden said, alluding to an Al Gore initiative that attracted little excitement.
So Biden set his sights on fashioning himself into president's most influential adviser, aides and friends say, trying to integrate his staff with Obama's so as to maximize his footprint without creating a competing power center within the White House. Where Cheney had amassed a large national security team reporting to him, Biden returned some of those positions to the president's national security staff.
Nearly five years later, it's not hard to find signs that Obama has relied heavily on Biden and his staff at pivotal moments.
Obama called on Biden to lead his gun control campaign, a top priority at the start of the second term. The push in Congress failed, but the vice president emerged as a prominent voice for a signal liberal cause.
Obama has also turned repeatedly to Biden's brain trust to fill key roles. In January, Obama tapped longtime Biden aide Tony Blinken to be his own deputy national security adviser. The White House sent Biden's top foreign policy adviser, Jake Sullivan, to meet secretly this year with Iranian officials about a possible nuclear deal while Biden aggressively lobbied his former Senate colleagues to hold off on new sanctions.
And on Sunday, Biden will depart for a week in Asia to meet with key leaders in a region where Obama has prominently committed to ramp up America's influence. Biden's visit to China, Japan and South Korea comes two months after Obama had to cancel his own Asia trip because of the partial government shutdown, leaving the White House seeking ways to prove it's still serious about the Asia rebalance.
"Barack Obama was smart enough when elected president to know he didn't know everything," said Sen. Tom Carper, a Democrat who's known Biden since the 1970s and was his partner in Delaware's Senate delegation. "One of the things he didn't really have as good of a grasp on was our relationship with leaders around the world."
Inevitably, Biden has been consumed by lower-profile tasks as well, such as a series of visits to seaports to promote infrastructure and exports, and an engagement effort in Latin America - a region that's never been prominent on the White House's radar aside from the immigration debate.
Sen. John McCain, who ran against Obama and Biden in 2008, said were he in Obama's shoes, he would deploy Biden visibly to address the ongoing health care debacle.
"The whole administration is in trouble," McCain said in an interview. "The president's numbers are going down and I don't frankly know why he doesn't have Joe Biden out there trying to more visibly work this out."
The Arizona Republican also credits Biden with forging deals that Obama could not have achieved on his own, like the year-end agreement to avert the so-called fiscal cliff. But those previous deals haven't always aged well with Democrats.
When Biden was missing from October's efforts to avert and later end the government shutdown, some Democratic senators said they were concerned that if Biden showed up, he'd be too eager to save the day and would hash out a deal that would give away far too much.
The White House disputes that was the reason he wasn't heavily involved, arguing that Obama had decided he wouldn't negotiate and didn't want to send signals to the contrary.
Douglas Brinkley, a presidential historian at Rice University, said that as with "Obamacare," keeping a low profile on the shutdown helped Biden avoid what could be a political burden down the road.
"He stood out of the way," Brinkley said. "Anybody involved in the shutdown, whose name is synonymous with the shutdown, would have egg on their face."
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