The setting: An election-year State of the Union address before a hostile Congress. Since the last one, the world has changed fundamentally, a war with Iraq has ended, and the nation’s economy is fragile and worrying to a majority of Americans.

“Now to our troubles at home, they are not all economic, but the primary problem is our economy,” the president tells a prime-time audience. “There are certain things a president can do without Congress, and I am going to do them.”

President Obama? No. George H.W. Bush in his 1992 State of the Union address, delivered 10 months before voters made him a one-term president. No other president has been able to claim that dubious, single-term distinction in the last three decades.

That could change this year as Obama, his approval ratings low and joblessness high, can expect a tough fight for another term. His State of the Union address on Tuesday will serve as the highest profile argument for why he should keep his job.

But Obama’s task as he heads to Capitol Hill is a particularly difficult one. He is building a populist campaign message around his fight with an “obstructionist” Congress, only partly controlled by the opposition Republicans. He also will be making his case for another four years at a time when the economy, while showing signs of improvement, is still viewed by most Americans as a huge problem.

Obama’s message is aimed at dual audiences Tuesday — Congress, the target of his political animosity; and the American people, the target of his political ambitions. How he delivers the argument will test his rhetorical dexterity and set the tone for the year ahead. The next day he leaves Washington for a trip through five swing states where he will seek to amplify his State of the Union message.

“Governing is one thing, campaigning is another — and the latter becomes far more pronounced in an election-year State of the Union,” said Robert Dallek, a presidential scholar. “One of the themes you’ll hear is a failure of Congress. That could come in a call to stop thinking about politics and start thinking about the good of the nation. Of course, many of them don’t share that view and that’s where the tension in the room will lie.”

Obama’s senior advisers say he does not intend to shy away from his recent attacks on Congress or of the economic policies promoted by his Republican rivals, although he may sand off the sharp edges he has employed outside the Beltway in recent weeks to make his case.

Advisers say he will use the State of the Union to echo and expand on the economic themes he raised last month in Osawatomie, Kan., where he offered a populist defense of imperiled middle class ambitions. Many in his party believed it was his most effective economic address to date.

“Those were the themes, and this will be the blueprint for how to get there,” said a senior administration official, who spoke on condition of anonymity to discuss the direction the president will take. “It will be thematically consistent. But, as a State of the Union speech, stylistically it will be different.”

As a divided Congress weighs in with hisses or applause, Obama will be appealing to a more important audience beyond the chamber: the coveted independent voters who helped elect him in 2008 but have since cooled on his leadership.

Nearly two-thirds of independents disapprove of the way he has managed the economy, according to a recent Washington Post-ABC News poll, which also found that only 13 percent of independents approve of Congress.

Obama’s approval rating, now at 48 percent, has risen after he has spent months denouncing Congress, usually in important swing states, and outlining executive actions to get around recalcitrant lawmakers. But those executive actions, rolled out under the White House slogan “We Can’t Wait,” have grown steadily smaller in scope.

The October announcement in swing-state Nevada of a plan to help a million underwater mortgage holders has been followed since by ones to promote summer employment and, during a visit Thursday to Disney World in swing-state Florida, to encourage tourism.

That shrinking trend raises the question of how ambitious Obama intends to be in his State of the Union, which in past election years has been most successful when the chief executive sets out a thematic rationale for his policies rather than presenting a laundry list of new ideas.

“This was [President Bill] Clinton’s problem in a way — the lists of small-scale proposals can begin to look like you’re saving string, that you’ve run out of big ideas,” said Stephen Hess, a presidential scholar at the Brookings Institution. “You have come in and done big things, and at the end you’re left with an awful lot of odds and ends.”

Obama has lessons to learn from his four predecessors, who took different approaches in their election-year State of the Union appearances.

His advisers have read the recent election-year addresses with some saying that, in most cases, they are indistinguishable from those delivered in off years. Bill Clinton’s 1996declaration that “the era of big government is over” stands as an obvious exception, some Obama aides say.

Most previous recent presidents made a choice to look forward with a list of specific proposals for the year ahead — and, tacitly, a second term — or backward with a broad defense of their time in office. The most successful managed to balance the two.

When Ronald Reagan addressed Congress in 1984, unemployment stood at 8 percent, only half a percentage point below the current rate. But during the previous year, the economy had added 4 million jobs, and an unemployment rate above 10 percent at the time of the previous midterm election had declined quickly.

“I’m pleased to report that America is much improved, and there’s good reason to believe that improvement will continue through the days to come,” Reagan began, with characteristic optimism. The message evolved into his memorable campaign slogan, “It’s morning again in America.”

“Obama’s not going to be able to say that, so he has a more complicated task,” said William Galston, a senior fellow at the Brookings Institution, who served as Democratic Sen. Walter Mondale’s issues director in his 1984 campaign against Reagan.

Obama has been describing economic progress in his recent appearances, while acknowledging that the recovery is not creating jobs fast enough. He will likely continue with that cautious assessment in the State of the Union, given that the recovery has not given rise to the same optimism that Reagan reflected in his 1984 address.

“You have to rest this kind of narrative on things people believe are true because they are felt in people’s everyday experience,” Galston said. “You can persuade people on certain propositions, but it’s harder to persuade them on experienced-based facts. They have to be true.”

The election-year State of the Union delivered by George H.W. Bush in many ways was the most ambitious, containing a literal one-through-seven list of new initiatives to improve the economy. But scholars say that it failed to present a story of his presidency persuasive enough to overcome doubts about where he was taking the country.

Like Obama, Bush was able to announce enormous changes abroad that had occurred since his last State of the Union, most notably that “Communism died this year.”

Obama will be able to describe the revolutions of the Arab Spring, which has brought a more democratic, if less certain, political environment in the Middle East. He has also overseen the departure of all U.S. troops from Iraq, ending a long unpopular war.

But Bush, like Obama, faced an economy in crisis and deep doubts about his ability to fix it. He blamed Congress for its lack of help, and announced, as Obama has, a series of steps he would take on his own to boost the economy.

Presidential scholars say the list, while amounting to serious policy, came off as disjointed to many Americans, who did not embrace his argument for another term. Obama hopes to avoid that problem.

“He will float some ideas, then will lay out the details in the coming weeks, which likely says more about the nature of the media than it does about this president,” the senior administration official said, suggesting Obama will have to remind voters repeatedly what he has proposed. “The shelf life of an idea is much shorter in the era of Twitter.”

Outlining a defiant defense of his first term, George W. Bush used his 2004 State of the Union to frame the terms of his reelection effort, telling Congress that “we can go forward with confidence and resolve, or we can turn back to the dangerous illusion that terrorists are not plotting and outlaw regimes are no threat to us.”

Obama, too, has echoed that choice between past and present, only in economic terms.

In Osawatomie, he declared the failure of trickle-down economics, criticizing Republicans of “collective amnesia” for endorsing tax cuts for the wealthiest Americans. He warned about this “make-or-break moment for the middle class,” clearly aligning himself with their interests.

But Galston warns that Obama has to be careful using too much of that combative tone in a State of the Union address, even in an election year.

“You still have to present yourself as president of all the people, especially Obama, because that was the core promise,” Galston said. “The president isn’t just a candidate for the presidency, he’s the president. There are advantages that an incumbent has, including the State of the Union venue, but they can be squandered.”

Polling analyst Scott Clement contributed to this report.