WASHINGTON -- For President Barack Obama, the massacre of schoolchildren in Connecticut has upended standard political calculations and presented a choice that goes to the heart of his approach to governance, not just on guns but also on issues like climate change, immigration and even taxes.
Should he invest his energy and the stature he won with his re-election last month in a fight he may believe in but is not sure he can actually win? And with his last election now behind him, is he willing or even able to shift the dynamics in Washington to make such fights winnable?
To his core supporters, this is a moment that will define what a second-term Obama presidency will look like -- whether it will be closer to the soaring aspirations that set liberal hearts aflutter in 2008 or more like the back-room dealmaking that characterized the four years that followed. Advocates on the left have long lamented that Mr. Obama was too quick to compromise, even as those on the right see him as a champion of a radical agenda.
From his point of view, Mr. Obama has been pragmatic, making clear-eyed if cold assessments about when the votes were there and when they were not. Mr. Obama does not accept the notion that he has not pursued goals that seemed hard to achieve, most notably the historic health care program he pushed through. The economic crisis invariably forced other priorities onto the shelf.
But with the election over, outside events have now presented Mr. Obama with a series of decisions. Vote counts might suggest he is still a long way away from passing significant new legislation on climate change, immigration and gun control. But Hurricane Sandy, last month's Latino vote turnout for Democrats and now the Newtown shootings have also given him openings to make fresh arguments.
The developments in his fiscal negotiations with Republicans, overshadowed momentarily by the roiling gun debate, underscore the same tension. After agreeing to renew Bush-era tax cuts for the wealthy in his first term, Mr. Obama has stood firm against it on the eve of his second and forced Republicans to accept raising rates on high income. But he compromised last week by agreeing to exempt many of those he has deemed wealthy and faces a test on whether he will stick to that even as House Republicans readied an alternative proposal.
Although he has spoken out for gun control without putting muscle into it before, his emotional speech at a memorial service in Newtown last Sunday declaring that there was no longer any "excuse for inaction" suggested this time may be different. The pressure is high from pundits who compared the speech to Abraham Lincoln's Gettysburg Address and suggested Newtown may be what Birmingham was to John F. Kennedy in inspiring civil rights action.
"This moment is so pain-filled and there is such a desire -- I think you can feel it building -- to move forward in a common-sense way that he sees the imperative," said Melody Barnes, the president's former domestic policy adviser. "I've looked at the pictures of his face, and I think he sees that there's no other course than to move forward. The situation demands it."
Yet the normally sure-footed White House has seemed uncertain how far the president really intends to go. Aides who normally offer expansive explanations of Mr. Obama's thinking have declined to return phone calls. On Monday, Jay Carney, the White House press secretary, generally stuck to repeating the president's words from his speech in an effort to avoid boxing him in, and he tamped down expectations of instant action by using the phrase "in coming weeks" 16 times.
Then, later in the day, the White House confirmed that Mr. Obama had met with Vice President Joe Biden and three Cabinet secretaries to discuss gun control and other responses to the tragedy, but declined to provide details. Even the simple question of whether the president put Mr. Biden in charge of developing a response went unanswered by a half-dozen White House aides questioned on Tuesday. Mr. Biden headed to his home in Wilmington, Del., without commenting.
The White House opened the window a little on Tuesday, hinting at the kinds of gun measures Mr. Obama would embrace. In the past, he has endorsed reinstatement of an expired ban on assault weapons, but this time, Mr. Carney said, the president would be "actively supportive" of a fresh legislative effort. The president will also support closing the so-called gun show loophole (exempting gun buyers in certain circumstances from required background checks) and "potentially" limits on high-capacity ammunition clips of the sort used in Newtown, Mr. Carney said.
But Mr. Carney said the president hoped to forge a broader response than just gun regulation, including looking at mental health, education and cultural issues.
These decisions are made on a scale of trade-offs that may be unique to the White House. President Bill Clinton made big pushes in his early days for priorities that did not have the votes, or that helped cost Democrats the Congress in his first midterm election, including the assault weapon ban that later expired and left the party feeling burned for nearly two decades. Then Mr. Clinton adjusted and focused more on making incremental progress toward his goals.
President George W. Bush scorned what he considered Mr. Clinton's "small ball" approach and prided himself on bold initiatives like cutting taxes, remaking education, expanding Medicare to cover prescription drugs and combating AIDS in Africa. But by his second term, he pursued big goals such as overhauling Social Security and immigration only to lose.
"There certainly can be a cost to it," said Peter Wehner, a White House adviser to Mr. Bush who worked for Mitt Romney this year. "You can fight for something and lose and be a weakened figure. On the other hand, sometimes there's honor in loss. You may lose but in the process you advance a cause in the eyes of history."
Mr. Wehner and other conservatives consider the groundswell for gun control to be understandable but more a symbolic gesture than an effective response. But he said Mr. Obama had been smart about picking the terrain he fought on. "He has waited until the stars aligned before he acted," he said.
In the end, the stars have not aligned before for Mr. Obama priorities like legislation on climate change and immigration. He took office amid the worst economic crisis in generations and pursued a historic health coverage expansion that had eluded his predecessors. By the time he pushed that through, enacted a stimulus package, toughened Wall Street regulations and lifted limits on gays in the military, he had lost the House and did not think the new Republican majority would agree to gun legislation.
"The president always had a personal commitment to the issue," said Phil Schiliro, who was Mr. Obama's first legislative affairs director. "But given the crisis he faced when he first took office, there's only so much capacity in the system to move his agenda."