The first major test of President Obama's second term has come early -- and it's one he must ace if he hopes to push through an ambitious second-term agenda that could prove as contentious as the current gridlocked financial negotiations.

Obama returns early from his Hawaiian vacation Thursday to restart negotiations with Republicans. But with only days remaining to avoid the massive tax increases and spending cuts that experts said could throw a still-weak economy into a recession, there's broad concern that both the White House and Congress are still too far apart to reach a compromise in time.

For Obama, the stakes in the "fiscal cliff" negotiations are even greater. The president was criticized by supporters early on for caving in too quickly to Republican demands and for failing to deliver on campaign promises like closing the Guantanamo Bay prison.

Those same supporters are now watching to see if the president's re-election has given him the clout he needs not just to settle the current dispute, but other key issues, like gun control and immigration reform, which are expected to dominate his second term.

"The buck stops with Obama. He is the head of government, and fundamentally, it's his responsibility to find a solution rather than apportion blame to others," GOP pollster Whit Ayres said. "He could demonstrate an ability to find common ground but he seems to have little interest in doing so."

Obama has been far more personally engaged and assertive in his dealings with Republicans on the fiscal cliff than in past negotiations over taxes and spending. Some experts said that's because the president has little to lose, as polls show most Americans are set to blame Republicans for any failure to strike a deal.

"I think this is the Y2K for 2013," Democratic strategist Christopher Hahn said. "After Jan. 1, the world isn't going to end. We'd go back to the Clinton-era tax rates. That's what many people want."

Still, economists have predicted that plunging over the fiscal cliff would cost the average family $3,500 in higher taxes next year and potentially cause another recession.

"In terms of him really improving his legacy overnight, he needs to work out a deal," said Susan MacManus, a political scientist at the University of South Florida. "It makes the rest of his initiatives easier. And his legacy is dependent on him being able to fix the economy."

Obama had hoped to reach agreement on the cliff by Christmas, in part so he could focus on other areas of his second-term agenda. He promised gun control proposals by January and vowed to pursue comprehensive immigration reform, which eluded him during his first term in office.

For the president, a political win heading into the new year is just what he needs for leverage in looming debates, analysts said.

"It's never going to be a slam-dunk for Obama," MacManus said. "The House is always going to be a problem for him. But it could get even worse depending on how [the fiscal cliff talks] turn out."