WASHINGTON -- For the first time since the war in Iraq began, more than half of the American public believes that the fight there has not made the United States safer, according to a new Washington Post-ABC News poll.

While the focus in Washington has shifted from the Iraq conflict to Social Security and other domestic matters, the survey found that Americans continue to rank Iraq second only to the economy in importance -- and that many are losing patience with the enterprise.

Nearly three quarters of Americans say the number of casualties in Iraq is unacceptable, while two-thirds say the U.S. military there is bogged down, and nearly 6 in 10 say the war was not worth fighting -- in all three cases matching or exceeding the highest levels of pessimism yet recorded. More than 4 in 10 believe the U.S. presence in Iraq is becoming analogous to the experience in Vietnam.

Perhaps most ominous for President Bush, 52 percent said war in Iraq has not contributed to the long-term security of the United States, while 47 percent said it did. It was the first time a majority of Americans disagreed with the central notion that Bush has offered to build support for war: that the fight there will make Americans safer from terrorists at home. In late 2003, 62 percent thought the Iraq war aided U.S. security, and just three months ago, 52 percent thought so.

Overall, more than half -- 52 percent -- disapprove of how Bush is handling his job, the highest of his presidency. A somewhat-larger majority -- 56 percent -- disapproved of Republicans in Congress and an identical proportion disapproved of Democrats.

There were signs, however, that Bush and Republicans in Congress were receiving more of the blame for the recent standoffs over such issues as Bush's judicial nominees and Social Security. Six in 10 respondents said Bush and GOP leaders are not making good progress on the nation's problems; of those, 67 percent blamed the president and Republicans, while 13 percent blamed congressional Democrats. For the first time, a majority, 55 percent, also said Bush has done more to divide the country than to unite it.

The surge in violence in Iraq since the new government took control -- 80 U.S. soldiers and more than 700 Iraqis died in May alone amid a rash of bombings -- has been accompanied by rising gloom about the overall fight against terrorists. By 50 to 49 percent, Americans approved of the way Bush is handling the campaign against terrorism, down from 56 percent approval in April, equaling the lowest rating he has earned on the issue that has consistently been his core strength with the public.

That is the view of poll respondent Margaret Boudreaux, 63, a casino worker living in Oakdale, La. "I don't think it's going well; there's too much killing," she said, worrying that the Iraq invasion could move more enemies to violence. "I think that some of the people, if they could, would get revenge for what we've done."

"You hear a lot about Saddam but nothing about Osama bin Laden. I don't think he [Bush] does enough to deal with the problems of terrorism. ... He's done a lot of talking, but we haven't seen real changes," said another poll respondent, Kathy Goyette, 54, a San Diego nurse. "People are getting through airport security with things that are unbelievable. ... I don't think he learned from 9/11."

The poll suggests that views on the Iraq war's impact also remain highly partisan. Three in 4 Republicans said the Iraq invasion has boosted domestic security, while 3 in 4 Democrats said it has not. Political independents lean negative on the issue: About 6 in 10 said the war has not made the United States safer.

Overall, Bush's 48 percent job approval rating was essentially unchanged from the 47 percent rating he received in a late April poll. And there was growth in the proportion of people who said the economy was doing well: 44 percent, up from 37 percent in April.

A total of 1,002 randomly selected adults were interviewed by phone June 2-5 for this Post-ABC News poll. The margin of error for the overall results is plus or minus 3 percentage points.