Last week's Democratic convention in the U.S. boosted voters' views of John Kerry but failed to give him the expected bump in the race against President Bush, a USA TODAY/CNN/Gallup Poll finds.

In the survey, taken Friday and Saturday, Kerry trailed Bush 50%-46% among likely voters. Independent candidate Ralph Nader was at 2%.

The survey showed Kerry losing 1 percentage point and Bush gaining 4 percentage points from a poll taken the week before the Boston convention.

The change in support was within the poll's margin of error of +/�C4 percentage points in the sample of 763 likely voters. But it was nonetheless surprising, the first time since the chaotic Democratic convention in 1972 that a candidate hasn't gained ground during his convention.

USA TODAY extended its survey to Sunday to get a fuller picture of what's happening.

A Newsweek poll taken Thursday and Friday gave the Democrats a 49%-42% lead. Over three weeks, that reflected a 4-point "bounce" for Kerry, the smallest ever in the Newsweek poll.

Among registered voters in the USA TODAY poll, Kerry and Bush each had 47%. Bush was up 4 points, Kerry unchanged from the pre-convention survey.

Analysts say the lack of a bounce may reflect the intensely polarized contest. Nearly nine of 10 voters say their minds are made up and won't change. "The convention, typically a kicking-off point for a party, is now merely a reaffirmation" of where voters stand, said David Moore, senior editor of the Gallup Poll.

"In a race this tight, the polls are going to be all over the place," said Kerry spokeswoman Stephanie Cutter. "Most importantly, voters now clearly trust John Kerry more than Bush to lead and defend America."

But Matthew Dowd, chief strategist for the Bush campaign, said "history doesn't bode well" for Kerry. Since World War II, every challenger who has unseated a president has led after his convention.

Democratic leaders had expressed delight about the convention, which showed a united party and emphasized national-security issues. Those surveyed gave the convention and its candidate high marks:

* Kerry's acceptance speech Thursday was rated as "excellent" by 26%, a more positive response than Bush got four years ago at his convention. A 44% plurality said the Democrats were "about right" in criticizing Bush; 30% said they went too far.

* Views of Kerry's personal characteristics and leadership improved across the board; views of Bush didn't change much. Bush's edge in handling terrorism was shaved to 12 points from 18 before the convention. In a switch, Kerry is trusted more to handle the responsibilities of commander in chief, 51%-46%.

* Kerry's military service in Vietnam, a theme of the convention, is seen as a plus. A 52% majority says that experience would help him be an effective president. More than one in four say it makes them more likely to vote for him.

Source: Agencies