WASHINGTON -- He’s older. He’s grayer. The jaunty optimism about changing the world has given way to the sober reality of stubbornly high unemployment and economic anxiety. In his own words, President Barack Obama has “some dents and dings in the fender.”

Yet beneath those external differences, the question persists: How has Obama changed as a leader in the four years since he first accepted his party’s nomination for president as a young man with little executive experience and little history in Washington. Has he learned on the job? Has he been guided by core principles come what may, or has he changed to adapt to what’s become a vastly different political landscape? The answers could determine how successful he’d be in a second term.

In his first two years, Obama stayed the course and pushed an agenda through a friendly Democratic Congress to stimulate the economy, regulate Wall Street and overhaul health care. Yet he’s maintained much of that course even as the country balked at his health care law, as voters threw his party out of power in the House of Representatives, and as his agenda has stalled ever since.

“On the one hand, he’s got a legacy,” said George Edwards, a scholar of the presidency at Texas A&M University, pointing to sweeping financial regulations and health care legislation sought by Democrats for decades. But Obama also displayed what Edwards called a “misunderstanding of leadership,” which put too much emphasis on his own powers of persuasion and led Obama to “overreach” on health care.

“As a result, he lost the ability to govern because he lost Congress and he’s not likely to get Congress back. Ever,” Edwards said.

To Obama and his inner circle, his steadiness is a critical virtue.

In his 2006 memoir, “The Audacity of Hope,” Obama wrote that he was not “somebody who gets real worked up about things.” His preference for “no drama” became an article of faith within his campaign – and at his White House.

He remains “the most steady, unflappable member of the entire team,” in the words of former White House aide Bill Burton.

“The traits that made him a good candidate, make him a good president,” said Burton, who left the White House in 2011 and is a senior strategist with a pro-Obama “super” PAC, Priorities USA Action. “He keeps the team steady and level headed.”

When Obama’s push for an overhaul of the nation’s health care appeared stalled in 2010, Rahm Emanuel, then the White House chief of staff, suggested the fight was costing too much and urged Obama to settle for less. “I told him many times (about) the political cost of doing this and, thank God for the rest of the country, he didn’t listen to me,” Emanuel said after the Supreme Court upheld the law in June. “That’s what political leadership is about,” added Emanuel, now the mayor of Chicago.

But where his advisers see consistency, others see inflexibility that in the face of rigid Republican opposition has hampered Obama’s efforts to pass more spending to stimulate the economy and create jobs.

William Galston, a top adviser in the Clinton White House and a current scholar at the Brookings Institution, a center-left think tank, said he believes Obama has learned much in office about how Washington works – but that he’s made few accommodations.