ASHINGTON - Suddenly, the context of the campaign shifted. The comfortable terrain of peace and prosperity was transformed, at least for a time, into darker turf.
A terrorist attack upon a US Navy destroyer ... televised images of Israeli helicopter gunships blasting away at Palestinian targets ... an oil shock striking Wall Street ... the Dow plummeting 379 points.
For Governor George W. Bush of Texas and Vice President Al Gore, and for voters weighing the choice between them, yesterday's events were an unsettling reminder that the world can still be a chaotic and dangerous place.
Both campaigns responded to the Mideast violence with calls for American unity and resolve, and partisan restraint.
''I'm not going to take any political questions,'' Gore told reporters. ''It's time for our nation to speak with one voice,'' Bush said. ''I appreciate the administration's efforts to bring calm to that troubled part of the world.''
The candidates were wise to take a nonpartisan approach, said presidential historian Charles O. Jones. ''George Bush has to be extra careful, as does Gore, about not seeming to be taking advantage of the situation,'' Jones said.
''Beyond that, the crisis introduces more uncertainty in what has come to be a very uncertain election. All of a sudden we have bad things happening in what we thought were good times,'' said Jones.
Americans historically have rallied behind their government in times of crisis. The shift in the political and media focus might therefore provide some short-term benefit to the vice president.
''Whoever is responsible will be met with a full and forceful and effective retaliation by the United States,'' Gore vowed, in a speech in Milwaukee. ''We will defend our country and we will defend our democracy.''
After his rhetoric at the Wisconsin rally, Gore curtailed his campaign swing and returned to Washington on Air Force Two to report for duty at the White House, where he was expected to meet with national security advisers. ''This is not about politics; it's about peace in the Middle East,'' said Gore spokesman Chris Lehane.
The round-the-clock coverage of the violence in the Middle East might also help Gore by turning the conversation on the campaign trail away from where it otherwise might be: on Bush's generally well-received performance in Wednesday night's debate.
The Texas governor has been climbing in opinion polls, and several instant surveys taken after the debate showed Bush ahead of Gore when respondents were asked who won the contest.
''I think the American people saw their next president last night in Governor Bush,'' said Bush communications director Karen Hughes.
The Bush campaign took special satisfaction from the fact that the crisis occurred after the governor's assured responses to foreign policy questions during the debate.
''I think I may have surprised some people about my ability to converse'' on foreign policy, Bush said in a CBS television interview. An international crisis might otherwise have fed doubts about Bush's inexperience in foreign affairs, his staff said.
Yesterday, Bush was confident enough to use the attack upon a US Navy destroyer, the USS Cole, as an example of the dangers of the post-Cold War world, and proof that the United States should develop an antiballistic missile system to defend itself from attacks by terrorists.
Bush began his day yesterday with an unusual early-morning statement to reporters in which he labeled the assault on the Cole ''a cowardly attack,'' and called for peace in Israel.
''Chairman Arafat must stand up and call upon the people he represents to put down their rocks and arms. He must take a leadership role to quell the violence,'' Bush said. ''It's time for him to be a statesman.''
Later in the day, before delivering a speech at Neshimany High School in Langhorne, Pa., Bush asked for a moment of silence for the sailors killed in Yemen. ''May God bless them and their families,'' he said, and many in the audience of 3,000 replied ''Amen.''
The attack on the destroyer is not likely, by itself, to dominate the campaign for the four weeks leading up to the election. But continued strife, and Wall Street's reaction, could be a troubling sign for the Democrats.
A prolonged stock market slump, or an energy crisis brought on by extended violence in the region, could dent one of Gore's most potent arguments: that voters would be wise to stick with the Democrats to extend good economic times.
''If the crisis doesn't last, I don't see it having a measurable effect,'' said Richard Haass, the director of foreign policy studies at the Brookings Institution. ''If it does last and it gets worse, if you have more violence, if the price of oil climbs, if there is additional terrorism and the stock market is roiled, I think it would hurt the vice president.''
Globe Staff writers Glen Johnson, traveling with Bush, and Susan Milligan, traveling with Gore, contributed to this report.
