WASHINGTON: Four years ago Barack Obama was a fresh-faced political sensation who had not even served a full term in the Senate and was about to become one of the youngest presidents ever.

Now he is 51, his hair more gray, his face more lined. He’s the parent of a teenager and a pre-teen. His blood pressure has ticked up a bit, although it’s still excellent. He’s quit smoking. He’s a dog owner.

The changes in the president aren’t just physical. As he enters Term Two, he is also sounding more confident, vowing a harder line on negotiations, relying more on trusted allies, promising less and expressing more cynicism about the grip of partisanship on Washington.

And perhaps most important, he seems more convinced of a need to keep average Americans with him, coming full circle to his 2008 grassroots campaign.

“You can’t change Washington from the inside,” he said during his re-election campaign. “You can only change it from the outside.”

On the best days of his presidency, Obama has been witness to the power and possibilities of the office he holds. On the worst, he’s seen its limitations.

He has celebrated passage of his transformative health care overhaul and mourned the children massacred at a school in Newtown, Connecticut.

He has savored the news that Osama bin Laden at last had been brought down. And he stood vigil over the remains of fallen soldiers returned to the U.S.

Between the highs and lows came the daily grind of a daunting job whose demands never end. There is always one more negotiation. One more legislative tussle. One more economic soft spot. One more natural disaster.

By all accounts, Obama’s style and his character remain largely unchanged. But every chapter of his presidency – the gasp-inducing early economic crisis, the battle over health care, the midterm congressional shellacking, the mass shootings in the past year, the endless negotiations over debt and deficit, the re-election brawl – has helped to mold him and to shape his perspective.

“Four years in, he has a very good sense of the job,” says senior adviser Valerie Jarrett. “He has a great sense of what is possible if you do have the American people behind you and willing to push with you to make change.”

Change has not come easily in Washington, however, which remains as divided as ever. Republicans largely blame Obama’s wrong-headed presidential policies and unyielding tactics for the persistent partisanship. And some in the president’s own party wonder whether his new, tougher rhetoric truly will result in firmer stands.

The public, for its part, has revised its own assessment of Obama over the past four years.

Polls show the president is still regarded as a good communicator, friendly, well-informed, caring, trustworthy. But there’s been a significant slide in the share who see him as a strong leader and as someone who can get things done.

Andrew Kohut of the Pew Research Center thinks Obama’s numbers on that count are due to rebound somewhat, given recent improvement in his approval ratings. His approval numbers are back in the mid-50s after dipping into the 40s at times in 2011 and 2012. But they’re still nowhere near the 60s and 70s of his first few months in office.

The president himself came out of his re-election victory convinced he has a stronger hand, and eager to use it before power inevitably ebbs later in his second term. He says he won’t negotiate with Republicans on raising the debt limit. He’s used his executive powers to act unilaterally to try to reduce gun violence.

That emboldened re-election outlook is coupled with a determination to stay above the day-to-day fighting in Washington’s trenches and to keep the public with him.

In announcing a package of proposals this week to reduce gun violence, the president did what he could on his own, but also acknowledged that the most important provisions require congressional approval, and said it would take a demanding public to make that happen.

“His audience has become much more the American people than the people who live within the confines of Washington,” says former Obama spokeswoman Jennifer Psaki.

The Brookings Institution’s William Galston, who served in the Clinton White House, says Obama seems to have concluded that getting too involved in the details of legislation was a mistake.

His more hands-off approach to the latest negotiations over taxes “might be seen as a new paradigm,” Galston says. “The president is not spending a lot of time with his sleeves rolled up, face to face with people who disagree with him.”

Nor is he making as many promises. After making more than 500 specific promises in his first campaign – more of them kept than broken – the president served up far fewer re-election pledges and has displayed a more measured view of what’s possible.

He’s a “happy warrior” the president says of himself, but he also admits to disappointment that he hasn’t gotten more cooperation from Congress.

Some liberals who complained that the president wasn’t tough enough in the first term look at his recent decision to give more ground than expected in extending Bush-era tax cuts to some wealthier Americans and wonder if he’s really stiffened his spine for term two.

The president’s renewed determination to leverage public support appears to be coupled with a willingness by the no-drama president to show more emotion when matters of public policy are also personal to him.

Hours after the massacre of 20 children in Newtown a tearful Obama showed raw grief in his first comments on the attack, calling it the worst day of his presidency. His temper flared after Republicans criticized U.N. Ambassador Susan Rice over the deaths of four Americans during an attack on a U.S. Consulate in Libya, insisting her critics “should go after me” instead.