WASHINGTON -- Barack Obama approaches his second term confronting tough and shifting challenges that will play big roles in shaping the rest of his presidency and his eventual place in history.
In the coming months, Obama will have to decide where to be ambitious, where to be cautious, and where to buy time.
Some of the big issues awaiting the president's decisions are familiar, long-simmering problems, including immigration and the need for a tenable balance between taxes, spending and borrowing.
Gun control jumped to the top of the national agenda after the massacre of first-graders and teachers at Sandy Hook Elementary School in Connecticut. And the issue of climate change remains unresolved.
"Americans are yearning for leadership," said Gil Troy, a presidential scholar at McGill University.
Other presidential historians cautioned that Obama is severely constrained by political realities, noting that he will have to carefully pick and choose which goals to emphasize in his second four years.
"I see Obama as almost uniquely handcuffed by circumstances," said John Baick of Western New England University. The number of big, unresolved problems facing the nation, coupled with a deeply divided public and Congress leave Obama with fewer viable options than most presidents have enjoyed, he said.
At best, Baick said, the U.S. government "is a gigantic cruise liner, and the most he [Obama] can do is keep us from hitting icebergs."
Obama said last week that gun control will be a central issue in his second term. "I will use all the powers of this office to help advance efforts aimed at preventing more tragedies like this," he said of the Sandy Hook Elementary School mass killings.
Political observers say Obama's first priority is to resolve the deep partisan divide over tax-and-spending issues, exemplified by repeated impasses over two years that led to this week's showdown on the "fiscal cliff."
An even higher-risk conflict may arise in a few months. Congress again must either raise the federal debt ceiling or see the government default on its loans.
Beyond that, lawmakers and interest groups are watching for signs of how hard Obama might push to restrict firearms and expand illegal immigrants' rights.
But Americans' affinity for firearms runs deep, and many political activists think Obama could have more sweeping success with immigration changes.
He won a large majority of Hispanics' votes in both his elections.
Chris Dolan, a political scientist at Lebanon Valley College in Pennsylvania said he expects Obama to be "incredibly ambitious on comprehensive immigration reform." The effort, Dolan said, could "build a lasting Democratic support group. You can't do that with gun control."
Still, opposition to granting citizenship to illegal immigrants runs deep in many circles, especially the Republican Party's base. Bids for "comprehensive immigration reform" have gone nowhere in Congress in recent years.
But Doris Meissner, a former commissioner at the U.S. Immigration and Naturalization Service, said that even with a full plate of challenges and a hostile party controlling the House, "I think Obama absolutely has to go big on immigration."
The White House has declined to detail the president's plans for a second-term agenda.
Once the deficit-spending problems with the fiscal cliff are addressed, "President Obama looks forward to working on a number of issues that are critical to our future, from immigration to energy, to education and national security direction," said White House spokeswoman Jamie Smith.