WASHINGTON - Agence France-Presse

As he prepares to bask in the Hawaii sun on a much-needed break from the White House trail, Barack Obama threatens to be disturbed by a new problem from an old source of vexation: Hillary Clinton.
It is perhaps a coincidence that Clinton is back in the limelight just as the presidential hopeful finalizes his choice of running mate in the build-up to the Democratic convention starting on August 25.
Clinton professes no desire to intrude on Obama's vice presidential deliberations, but her diehard supporters are intensifying pressure to see their heroine rewarded for her dogged challenge for the Democratic nomination.
"There's this giant elephant in the room, Hillary Clinton, that he still has to contend with," said Costas Panagopoulos, director of the Center for Electoral Politics and Democracy at Fordham University.
"The party is fighting an uphill battle to unify itself and this would have happened no matter who was the nominee. There are a lot of unhappy Democrats still out there," he said.
With Obama jetting out for a weeklong family vacation in his birthplace of Hawaii, Clinton Friday staged her first solo rally on his behalf in Las Vegas.
Clinton ad:
Polls suggest the Democrat is locked in a tight race with Republican John McCain -- who is picking at Democratic wounds with a new campaign ad featuring one of Clinton's acerbic attacks on Obama from their primary tussle.
In an online chat with supporters Thursday, the New York senator refused to dwell on talk of her running as Obama's vice presidential nominee.
"I am going to continue to do whatever I can to help Senator Obama and Democrats across the country win in the November (elections)," Clinton said.
But the web chat underlined that Clinton remains a force to be reckoned with in the party. Many supporters professed gushing admiration of the former first lady, and spoke of their qualms that Obama may overlook her for the VP job.
Since bowing out of the Democratic race in June, Clinton has been appealing for donations to help erase her hefty campaign debts of 22.5 million dollars.
There has been much grousing from some of her backers that Obama is not doing more towards the debt relief effort, and grumbles that the offer of a prime-time speaking slot in Denver does not do justice to her influence.
Obama is considered to be loath to admit the Clintons' political baggage, staff infighting and personal agendas onto his tightly scripted presidential ticket.
But some diehard Clinton supporters are stepping up a campaign to get her name onto the nominating ballot at the convention, in a last-gasp effort to derail Obama's coronation.

Need for unified party:
Clinton last week appeared to back the idea of a roll-call vote in Denver, to register her nearly 18 million primary backers for the record, rather than having Obama nominated by acclamation.
But in her web discussion, she recapped a joint statement put out late Wednesday with the Obama campaign that stressed party unity but was studiously vague about any convention vote.
Briefing reporters on his campaign plane Thursday, Obama said he had spoken with Clinton this week and noted that she was set to campaign for him in Las Vegas and then in Florida just before the convention.
"She is very enthusiastic about the need for a unified party," he said, calling Clinton a "class act."
Convention arrangements were still being ironed out, Obama said. "But I don't anticipate any problems."
The Illinois senator also called Bill Clinton "very supportive," denying that the former president was being less than fulsome in his backing after his wife's bruising loss in the primary process.
Fordham's Panagopoulos said Obama ignores any unhappiness in camp Clinton at his peril. "I think he should be taking this very seriously as the last thing the Democrats want to do is project a divided image at the convention," he said.
"In this era of fragmented media and targeted communications, this is really the only time a presidential hopeful has a forum to speak to the nation as a whole."