WASHINGTON - Presidential terms are measured by sweeping laws and stirring events, but legacies are about enduring ideas. The one Barack Obama has in mind will drive most everything he tries to do in the next four years: assuring that America is a place where anyone can make it.

There is no moonshot here, no call to end tyranny in our time.

What Obama wants written in the first paragraph of history is that he helped deliver a better life for the people struggling in the richest nation on earth.

His second-term agenda amounts to a wish list in support of that core idea, and this time, he is freer to define the issues.

Obama wants an immigration law that would deal firmly but compassionately with millions of illegal residents; an economic model that demands more money from the rich to shrink the debt; a tax system that is fairer and simpler for families; and a bigger emphasis on education and made-in-America energy.

The old problem of gun violence is suddenly on the list now, too, but only after an elementary school massacre led Obama into days of reflection. He concluded that the country is failing its people in another fundamental way, by not keeping even its children safe.

This is the playbook of a Democrat who thinks the basic compact between a nation and its people has been broken, who sees government as more of an aggressive force for good than a bureaucratic menace to society.

In the discussions that shape Obama's next moves, in the speeches that convey his thinking, the policy premise is usually boosting hope and genuine opportunity.

Many people have lost both.

"I've got one mandate," the president said after defeating Republican Mitt Romney in November. "I've got a mandate to help middle-class families and families that are working hard to get into the middle class. That's what the American people said: 'Work really hard to help us.'"

The American people, however, also returned Republicans to power in the House, setting up a giant clash of visions over the role of government.

Should Obama get bogged down in power struggles over the debt and spending, his overarching ideas may be shrunk along with his legacy. His influence is limited by his opponents in Congress, forcing him to scale back time and again, and frustrating him about the pace of progress.

Yet piece by piece, he is building what he is convinced voters want. He will use his powers, he says, to build a country where "you can make it if you try."

He does not have much time. Presidential capital fades after the second year of a second term.

What Obama does have is more freedom to pursue an agenda on his terms.

By the time he is sworn in again Monday, Obama will have sworn off some of the problems he inherited.

The recession is over. So is the Iraq war, with the Afghanistan war winding down. Obama will never again have to worry about getting re-elected.

"He came into office when the American Dream was at its most maximum peril," said Obama confidant Robert Gibbs, recalling a collapsing job market and stock market. "Fixing that is likely to be a journey that will be the charge of the next several presidents. But it's his job to build a foundation."

Obama is halfway into that project.

It began with the milestones of his first term: a law extending health coverage to millions of people, taxpayer intervention to help a plummeting economy, consumer protections and Wall Street reform, and the appointment of two women to the Supreme Court, including the first Hispanic justice.

He also repealed the ban on gays serving openly in the military and became the first president to announce support of gay marriage.

Almost forgotten, by now, is the symbolism of Obama's presidency itself. He was the first black man to win the office.

"His progressive legacy is continuing the civil rights movements to the very last groups that have been marginalized," said Douglas Brinkley, a Rice University historian who has written extensively about presidents. "He is, in a way, trying to bring into the fold the last people who haven't made it."

Even when Obama looks back at the lowest moment of his re-election campaign, it is to bemoan his failure at explaining what his presidency is about. He told Time magazine that his flawed first debate against Romney never conveyed the stakes of a society in which too many have too little chance to succeed.

"Do we believe in an America that says some folks are more American than others or more worthy than others or more valued than others?" Obama said. "Or do we believe in an America where that Declaration (of Independence) means what it says: 'We hold these truths to be self-evident ... that all people are created equal?'"

Obama's legacy is already safe, Brinkley said, simply because he won again.

History is much kinder to presidents who got voter approval to finish what they started.

For Obama, Brinkley said, that means protecting Medicare, Medicaid and Social Security in a time when the country leans right-center and demands to contain the debt are soaring. "His role is to be the firewall," Brinkley said.

Even discussing one's legacy can be politically tricky for any White House.

The word itself can convey that the president is too focused on his place in history, or too close to nearing dreaded lame-duck status.

But Gibbs, who served as Obama's press secretary for the first half of the first term, said legacy-shaping is inherent in every big decision in the West Wing.

"People are exceedingly aware of the fact that, for better or worse, presidents are judged on their time in office," Gibbs said. "What are their ultimate, lasting contributions? Everybody understands that. Maybe it's the elephant in the room, but it's in each and every room."