US:Security around Barack Obama has tightened dramatically in the past week, so that everyone attending his events is now screened with a metal detector, as an expanded secret service detail watches the doors and sniffer dogs roam the venue, writes Denis Staunton
At the Rancho High School in Las Vegas this week, it took more than an hour for the crowd to pass through airport-style security and Obama's appearance was delayed further as the secret service screened off parts of the building before he took the stage.
None of the campaigns discuss security but the new measures surrounding Obama, which are much more elaborate than those for any other candidate and similar to those that accompany the United States president, are almost certainly a response to a heightened number of specific threats to his life.
They came as the issue of race moved to the centre of the Democratic presidential race, which last weekend saw sharp and sometimes bitter exchanges between the Obama campaign and that of Hillary Clinton.
The two candidates sought in Las Vegas to call a halt to the dispute, which was damaging both campaigns and threatened to poison relations within the Democratic party as a whole.
As the contest moves to South Carolina next week, however, where up to half of the Democratic primary electorate is black, it will be impossible to avoid discussing race, which remains the most sensitive issue in American political life.
Until last week, Obama seemed to many Americans to be a candidate who could help the US to move beyond its racial divisions, partly because of his background as the son of a white American mother and a Kenyan father. Unlike earlier African-American presidential candidates such as Jesse Jackson and Al Sharpton, he was not shaped by the civil rights struggles of the 1960s and has never presented himself as the representative of the African-American community.
His decisive victory in Iowa, which is more than 95 per cent white, appeared to prove he could overcome the prejudice that has blocked so many black political careers - or even that such prejudice was disappearing. Then came New Hampshire and the huge shift of support towards Clinton in the final hours before the primary. Struggling to explain why polls had predicted a big Obama victory up to the last minute, some commentators suggested that white voters had lied to pollsters about their voting intentions.
At the same time, Clinton and her husband, former president Bill Clinton, offended some African-Americans with remarks that appeared to disparage Obama's candidacy and to cast doubt on the historical role of Martin Luther King.
In the end, most white Americans were quick to give the Clintons the benefit of the doubt but African-Americans, who have endured coded racism and casual disparagement all their lives, saw things differently. In Las Vegas this week, Obama's wife, Michelle, put it neatly when she spoke about the difference a victory for her husband would make to African-Americans.
"The veil of impossibility will be lifted from the head of thousands of millions of kids like me and Barack who were told all of their lives, 'no, you can't, you're not ready, you're not good enough, your turn is later'. Our turn is now," she said.
The emphasis on race carries real dangers for Obama as the primary season progresses if white voters conclude that, rather than pouring a balm over racial divisions, his presidency could bring them to the fore.
Both candidates said this week that the election should not be about race but it may be too late now as white voters realise that electing Obama will not absolve centuries of racial injustice and African-Americans are reminded of James Baldwin's warning more than 40 years ago in The Fire Next Time: "Any upheaval is terrifying because it so profoundly attacks one's sense of one's own reality. Well, the black man has functioned in the white man's world as a fixed star, as an immovable pillar: and as he moves out of his place, heaven and earth are shaken to their foundations."
The most immediate damage has been done to Clinton, however, who saw 70 per cent of black Democrats in Michigan voting "uncommitted" this week rather than pulling the lever for her. Polls show South Carolina black voters breaking two to one in Obama's favour and that trend could prove decisive if it is followed on February 5th in other states with a large African-American vote, such as Georgia and Alabama.