Facing disappointing poll numbers among Jewish voters, Democratic candidate Barack Obama is doubling his efforts to win over older Jewish voters, mainly those in retirement communities in southern Florida.

Mr Obama's campaign has been sending surrogates to speak to Jewish voters in Florida and answer concerns they might have regarding the candidate's backgrounds and his views on Israel and the Middle East.

Those issues were brought into sharp focus by last Friday's debate between Mr Obama and rival Republican candidate John McCain in Mississippi.

Raising the issue of a nuclear Iran, Mr MCain vowed he would never allow "a second Holocaust" to take place, while Mr Obama called for tougher sanctions but insisted: "We also have to engage in tough, direct diplomacy."

Among those taking the trip to Florida recently was vice-presidential candidate Joe Biden, who promised Jewish voters: "I know in my guts, in my heart and in my head" that Mr Obama is a strong supporter of Israel.

Dennis Ross, the former Middle East envoy, and former New York mayor Ed Koch also took the tour to Florida's retirement communities.

The latest addition to the Obama Florida drive was an initiative called "The Great Schlep" launched by young Jewish Democrats, calling on young Jews to go and visit their grandparents in Florida and convince them to choose Mr Obama on November 4. The campaign drew attention thanks to a video clip starring comedian Sarah Silverman, known for her use of graphic language. "If you knew that visiting your grandparents could change the world, would you do it?" she asks in the clip. "Explain to them that we are all the same inside," she suggests.

The focus on Florida stems both from the role it plays as a swing state that might possibly determine the outcome of the elections, as it did in 2000, and from the difficulty in getting older Jewish voters, who backed Hillary Clinton, to support Mr Obama.

Local activists complained of encountering a sense of hostility when trying to speak to Jewish voters about Mr Obama. Senator Frank Lautenberg and congressman Robert Wexler met tough and sometimes rude crowds when lobbying for Obama in south Florida.

"We need to recognise that there is a problem," said one activist, state senator Steven Geller.

A poll published by the American Jewish Committee found that Mr Obama was still struggling to reach out to Jewish voters. According to the poll, Obama has the support of 57 per cent of Jewish voters whereas Republican John McCain gets the support of 30 per cent.