Suddenly the presidential campaign's longtime front-runners are facing new challenges, and lower-tier candidates are climbing.
The decline of national security and the rise of economic concerns has scrambled the race in both parties, helping underdog candidates make a case for themselves and forcing the leaders to change their tactics.
Rudolph W. Giuliani and Hillary Rodham Clinton have built their campaigns around the argument that they would step into the Oval Office best-prepared to be a strong wartime commander-in-chief. They have belittled rivals and each other as weak or naive when it comes to dealing with enemies.
Now voters in both parties are looking less for strength than for candidates who can offer change or a more reliable adherence to each party's core values -- or simply for someone who feels more likable.
The shift has benefited Democrat Barack Obama and Republican Mike Huckabee, who in recent weeks have narrowed or closed the gaps in key early-voting states, challenging front-runners Clinton and Giuliani. And it has fostered the sense that both parties' nominations are up in the air, with Democrat John Edwards and Republicans John McCain, Mitt Romney and Fred Thompson all homing in on domestic issues to connect with voters, or emphasizing differences in leadership style.
"There has been a shift, a subtle shift," said nonpartisan pollster Scott Rasmussen. "You can overstate it, because Iraq and security issues are still important."
The shift helps explain why Clinton, the Democratic New York senator, and Giuliani, the former Republican mayor of New York City, have moved to retool their images before caucuses are held Jan. 3 in Iowa.
Each front-runner had been feeding off the other: Giuliani boosted his Republican credentials by attacking Clinton, and Clinton pointed to those attacks as evidence that her party needed a tested survivor of the brutal partisan wars of the 1990s.
But this week the two are talking more aggressively about working hard to solve problems on voters' minds.
Clinton is showing a softer side by featuring friends giving sentimental website testimonials about "the Hillary I know." And Giuliani, while still embracing the aura of strength he gained after leading New York through Sept. 11, is trying to broaden his image. In what his campaign billed as a defining speech over the weekend in Florida, Giuliani pledged to fight poverty, improve education, cut taxes and end illegal immigration.
It was no coincidence that Giuliani's address in Tampa -- a hub of moderate Republican voters in the crucial battleground state -- seemed to put his once-dominant theme of strength in a new context. Cautioning that "middle-class families feel that the American dream may be slipping away," Giuliani exhorted the crowd to "decide for optimism, not pessimism; for hope, not despair; for strength, not weakness; for victory, not defeat."
The public's mood shift has been detected in a number of surveys and is viewed by analysts as the result of the housing-sales slump, fears of recession and an ebb in violence in Iraq. In an ABC News-Washington Post poll released last week, 24% of adults ranked the economy and jobs as their most pressing concern in choosing a candidate, slightly higher than the 23% who said Iraq.
Last month, the same poll showed 29% ranking Iraq as their highest concern, compared with 14% who pointed to the economy and jobs.
In New Hampshire, with voting set for Jan. 8, more than one in five Republican voters surveyed for Fox News ranked the economy as their leading concern, compared with 14% who listed the war. Immigration was the second most-cited issue in that poll, at 16%.
And in Florida -- which holds its primary Jan. 29 and has long been considered Giuliani's strongest early-voting state -- one survey by Rasmussen Reports showed Huckabee not only leading Giuliani overall but also among voters who claim to care most about Iraq.
Those voters did not seemed worried about Huckabee's lack of foreign-policy expertise, nor does Huckabee seem nervous about alluding to his own inexperience. Referring to a popular hotel advertising campaign, Huckabee jokingly told radio talk show host Don Imus this month that although he lacks a significant history with foreign affairs, "I did stay at a Holiday Inn Express last night."
The shifting landscape is triggering far different responses in each party.
For Republicans, the campaign has turned largely to a debate over which candidate would be tougher on illegal immigration and more apt to cut taxes. For Democrats, the candidates are bickering over who would do the most to transform Washington, and whose healthcare plan would cover the most uninsured Americans.
Two years ago, then-White House advisor Karl Rove designed a midterm election strategy with national security at its core that would differentiate between Republicans' "post-9/11 worldview" and a "pre-9/11 worldview" held by Democrats.
But Rove signaled last month that times have changed, writing in his newly launched Newsweek column that GOP candidates should "tackle issues families care about and Republicans too often shy away from. Jobs, the economy, taxes and spending will be big issues this campaign."
Until recently, it appeared that war and security would dominate the campaign. In September, Giuliani led the attacks on the liberal group MoveOn.org for its newspaper ad that mocked the U.S. commander in Iraq, Gen. David Petraeus, as "General Betray Us."
Democrats also sought to focus on the war, with Obama and Edwards assailing Clinton for her 2002 vote authorizing the invasion of Iraq. Clinton managed to find an advantage in that vote, which helped her build an image of strength on foreign policy. Some of Clinton's most effective moments in the debates this summer came when she attacked Obama as naive for his willingness to meet unconditionally with the likes of Iranian President Mahmoud Ahmadinejad and Cuban President Fidel Castro.
Surveys at the time showed that Clinton had amassed a huge advantage when voters were asked which candidate exhibited the most strength and which was best equipped to end the war in Iraq.
Despite the shifting dynamic, Clinton and Giuliani continue to lead in most national surveys, and they boast large organizations. Clinton is particularly strong, leading Obama by double digits in most national surveys. She posts high marks from voters when asked which Democrat can best lead on the economy, healthcare and other domestic issues.
But strategists for Edwards and Obama believe they can exploit Clinton's relatively high negative ratings by painting her as a status-quo candidate at a time that voters want something completely different, particularly on the domestic front.
"It's all started to spin in the direction of who's really going to change the way things work in Washington," said Joe Trippi, an Edwards strategist.