The party's convention opened yesterday in New York with an address by the relatives of three of the victims, who paid tribute to those who died, and a speech by the former mayor, Rudolph Giuliani, whose national prominence soared as a result of his leadership in the city following the terrorist attacks in 2001.

Comparing George Bush's leadership to Winston Churchill's role in Britain during the second world war, Mr Giuliani was due to say last night: "In times of danger, as we are now in, Americans should put leadership at the core of their decision. George W Bush sees world terrorism for the evil that it is."

But in the New York Times poll of victims' relatives, half said they believed the Republicans should not have held their convention in New York, and a quarter accused the Republican party of choosing the city "to capitalise on September 11". A quarter said they believed the party chose New York in order "to support the city".

"I'm not shocked that they would do this," said Don Johnson, who lost his brother-in-law, Bill Kelly, in the terrorist attacks. "But I think it's wrong. I don't think Bush showed good leadership after 9/11. I think he used it to curtail civil liberties and make families elsewhere in the world, as well as us, less safe."

The focus of last night's speeches represented an attempt to shift the public's focus to Mr Bush's finest hour, said Jennifer Donahue, a political scientist at New Hampshire political institute.

"The Bush administration is trying to take the Americans back to the days after September 11 because they believe it is the best example of Bush's leadership," she said.

"They want to change the subject away from the war and international relations and back towards the steadiness under fire that Bush executed during that time and in the public mind. That's why they chose New York and that's what Giuliani represents."

The convention is being held late in order to take place as close as possible to the third anniversary of the attacks.

The Vice-President, Dick Cheney, set the tone for the week on Sunday evening with a speech on Ellis Island during which he invoked Mr Bush's conduct after the attacks.

"[People] saw a man calm in a crisis, comfortable with responsibility and determined to do everything necessary to protect our people," he said.

Mr Giuliani said it was natural to dwell on the president's performance at such a critical time. "It's impossible to conduct this presidential election without talking about September 11," he said in an interview with USA Today. "It would be like conducting the re-election of Abraham Lincoln and not talking about the civil war."

And the decision seemed to go down well with delegates. "We absolutely need to invoke September 11 in the convention," Richard Aguilar, a delegate from Minnesota, told the New York Times. "This election will determine how we fight a war on terror that began right here in this city."

But using the attacks to bolster his image could backfire, said Ms Donahue. "There's always a risk in using a crisis for political situation that it could be perceived as opportunistic. They have some cover in Giuliani because there is a direct link between him and the events. If they used a member of the administration it would look more overt."

New York State's Republican governor had tried to arrange for the new building at Ground Zero to be laid during this year's convention, but brought it forward to July 4 after it became clear it would not be well received.

"If you were to do something overtly political around Ground Zero, you'd get hammered for it, and rightly so," Michael McKeon, a Republican strategist told the New York Observer recently.