The sense of unity that swelled across the country in the wake of the Sept. 11, 2001, terrorist attacks faded, and heated rhetoric and finger-pointing returned as America edged closer to the 2004 presidential race.
"Cynicism is back in full force. Extraordinary political partisanship and acrimony are back," says David Blankenhorn, president of the Institute for American Values, a think tank focusing on family and civil society.
Politicians traded insults and clashed over tax cuts and Medicare reforms, pro- and anti-war supporters rallied in the streets, and social activists faced off before the U.S. Supreme Court this year.
Political divisions in America are becoming more pronounced as the two major parties grow more polarized, according to Andrew Kohut, director of Pew Research Center for the People & the Press.
"We're seeing more differences between Republicans and Democrats on issues than we have since the mid-1980s," he says. The split is evident on a wide range of topics, including social spending, religion and the war on terrorism.
A recent Pew poll, for instance, found that 72 percent of Republicans favor a government policy of holding suspected terrorists without trial - a view held by just 46 percent of Democrats surveyed.
Americans - whose last presidential election ended in a virtual tie - have long split over social issues as well and this year their differences played out in different arenas:
Affirmative action supporters hailed a Supreme Court ruling that race can be one of the factors colleges use to choose their students.
Gay rights advocates celebrated landmark state and federal legal victories and the first openly gay bishop in the Episcopal church.
Right-to-life activists applauded President Bush's signing of a new law restricting certain abortions, which was promptly challenged.
Other contentious issues came to be identified with individuals.
Alabama Chief Justice Roy Moore tested the firewall between church and state and was ousted when he refused a federal court order to remove a Ten Commandments monument from a government building. He plans to appeal to get his job back.
Terri Schiavo, a severely brain-damaged woman in Florida, personified the anguishing debate over the right to die in a family dispute that escalated into a court battle that eventually involved Gov. Jeb Bush and the state Legislature.
All these social issues have been on and off the nation's radar for decades, but this year the public had one more reason to disagree: the war in Iraq.
"There was great unity around the war in Afghanistan but great divisiveness around the war in Iraq," says Blankenhorn, of the Institute for American Values. "There's a great uneasiness. People are dying every day."
Many recent polls have shown the nation is fairly evenly divided on how President Bush is handling Iraq - a significant drop from April, the month after fighting began, when a CBS poll, for instance, showed a 75 percent approval rate. (On the other hand, support for Bush's campaign against terrorism remains strong, with almost two-thirds approving in several polls.)
A USA Today-CNN-Gallup poll taken in December, after the president's Thanksgiving trip to Baghdad, showed six in 10 of those surveyed approved of the decision to go to war - the highest level of support since August.
Earlier polls, taken when the headlines were dominated by reports of mounting U.S. casualties in Iraq, suggested growing disenchantment with the war.
An early November ABC News-Washington Post poll found 54 percent of Americans saying the war was worth fighting - a drop from 70 percent in late April. That poll also found 58 percent of those surveyed said U.S. military forces should remain in Iraq until civil order is restored regardless of casualties, a decline from 72 percent in July.
"I think there's a concern that this will be a quagmire and it will go on forever ... and we're paying the cost of it in dollars and lives," says Robert Shapiro, a political scientist at Columbia University who specializes in public opinion.
Shapiro says the dwindling support also is tied to growing skepticism about the Bush administration's claims that Iraq had weapons of mass destruction, one of the justifications for toppling Saddam Hussein.
Beyond all the polls and political bickering, there were poignant reminders, too, in the heart of America of how divisive the war can be - even within individual families.
When Army 1st Lt. Brian Slavenas, a Chinook helicopter pilot killed in Iraq, was buried in Illinois in November, his divorced parents honored him in different ways.
His mother rejected a military funeral and publicly blamed President Bush for her son's death. His father, a veteran, defended the president and attended a ceremony with American flags, a helicopter flyover and a rifle salute.
It didn't always take life-and-death matters to polarize people in 2003.
One of the biggest rifts occurred in the Episcopal Church with the elevation of V. Gene Robinson, the first openly gay bishop consecrated by a major Christian denomination.
Another split over gay-related issues occurred last summer when the U.S. Supreme Court struck down a Texas law that made homosexual sex a crime.
The 6-3 decision was cheered by gay-rights advocates and denounced by conservatives.
"The court has taken sides in the culture war," Justice Antonin Scalia wrote for the three dissenters, suggesting the ruling would invite laws allowing same-sex marriages.
This fall, Massachusetts' highest court took on that very issue, ruling that it is unconstitutional to deny same-sex couples the right to marry and giving legislators six months to rewrite the state's marriage laws.
Canadian courts also legalized gay marriage over the summer.
Kohut, of the Pew center, says while polls show a liberalizing trend toward acceptance of homosexuals, it doesn't extend to gay marriage.
"That seems to be a line in the sand that the American public doesn't want to cross," he says.
A Pew poll released in November found opposition to gay marriage has grown since midsummer, with 32 percent favoring it and 59 percent against it. In July, 38 percent approved and 53 percent were opposed.
Americans also are split over abortion rights, always a politically charged issue that made headlines this year when Congress passed and Bush signed a bill that bans certain late-term abortions.
An NBC News-Wall Street Journal poll released in November found 47 percent of those surveyed favored and 40 percent opposed the ban.
Hundreds of anti-abortion opponents rose to applaud the president even as abortion rights activists mobilized to challenge the new federal ban in court.
But a nation divided over social issues is not new or unusual, some pundits say, and they caution against exaggerating the impact.
"Americans want the same things for their families, communities, their country," says Karlyn Bowman, a public opinion analyst at the American Enterprise Institute. People generally don't "think about most of these issues as we go about our daily lives."
"The 9-11 moment was a very unique moment in our history, a unique coming together," she adds. "It's unrealistic to expect that to continue for a long period of time. We spar, we disagree, but we still go on."