WASHINGTON // Since kicking off his unlikely presidential bid almost 19 months ago, Barack Obama has used one word more than any other: change. "I know that I haven't spent a lot of time learning the ways of Washington," he told supporters on an icy winter afternoon in February of last year, when he first announced his candidacy. "But I've been there long enough to know that the ways of Washington must change."
Since then the six-letter word has become a fixture of his campaign, applied liberally in his stump speeches and tossed around with abandon during debates. The freshman senator often labels his opponents - Republican and Democrat - as "creatures of Washington", mired in partisan politics. But Mr Obama has opened himself to a new bout of criticism after choosing the veteran six-term senator Joe Biden as his running mate, a man who has served on Capitol Hill longer than all but six members of congress.
Almost as soon as the choice of Mr Biden had been made public, Republicans were throwing Mr Obama's favourite word back at him. Nancy Pfotenhauer, John McCain's senior policy adviser, told MSNBC News on Saturday that Mr Biden's selection "calls into question and jeopardises their whole message of change". He is "clearly a creature of Washington," Ms Pfotenhauer said, taking a term from Mr Obama's lexicon. "He's been in the senate longer than he has been out of government, if you will, and he does not have the reformer reputation, for example, that someone like Senator McCain has."
Republican operatives were not the only ones ready to pounce. Hours after the choice of Mr Biden was made public, major media outlets and bloggers made a similar point. "Barack Obama began the summer as he began the campaign: the agent of change," wrote Jennifer Rubin, a conservative blogger and contributor to Commentary magazine's "Contentions" blog. "With the summer drawing to an end, he has chosen a running mate who is as old school as they come and as familiar as a worn-out shoe."
There will be more of that to come, said John Weingart, associate director of the Eagleton Institute of Politics at Rutgers University, noting even the smallest crack in a pillar of Mr Obama's campaign will be irresistible to his rival. "I suspect the Republicans will try to say in a number of ways that Obama is pulling back on promises that he had made," said Mr Weingart, who maintained that Mr Biden still embodies the brand of change Mr Obama preaches.
Voters see Mr Obama's version of change as "a change away from bitter confrontation and partisan politics", Mr Weingart said. "Biden more than other Democrats is someone who is respected by both parties and someone who is known for focusing on policy issues, not on personal attacks." It remains to be seen, however, if Mr Obama can convince voters that the same change he peddles as a fresh-faced Washington newcomer can be reconciled with a white-haired statesman who took office the year before Watergate forced Richard Nixon out of office.
Rhodes Cook, an independent elections analyst based in Virginia, thinks the young senator can pull it off. "I don't think that it is so big of a problem because as the campaign has gone on, more and more questions have been raised over how much change people really want," Mr Cook said, adding that a change in the oval office, let alone political party, would be enough to satisfy most voters. "They don't want to throw away the baby with the bath water," he said. "It may be good to have a wise old head around who knows how Washington works and can help structure the type of change that may be the most desirable."
Besides, he said, Mr Biden is a youthful 65. "He defies what you think of a normal 65 year old," Mr Cook said. "He's a guy who seems almost boyish at times and he is very enthusiastic." Mr Biden seemed as much as he made his first joint campaign appearance with Mr Obama on Saturday afternoon, all but jogging across the stage after his name was announced. The word "change" was as prevalent as ever.
"For decades he has brought change to Washington, but Washington hasn't changed him," said Mr Obama as he introduced his new running mate. Mr Biden repeated the campaign keyword as he took his first jabs at his Republican rival, Mr McCain, whom he also considers a friend. "You can't change America when you support George Bush's policies 95 per cent of the time," Mr Biden said to uproarious applause. "You can't change America when you know your first four years as president will look exactly like the last eight years of George Bush's presidency."
In the short term, Democrats hope Mr Biden's selection and the upcoming Democratic convention will provide at least one kind of change: a new direction for the polls, which in recent days suggest Mr McCain is gaining ground. "If it was three months ago when he was a running a little better in the polls, would Obama have picked him? We don't know," said Mr Cook, the political analyst. "A month from now, when the circumstances change, will [Biden] still look like as good a choice as he does today? We will have to wait and see."