Obama's vice-presidential candidates

Hillary Clinton: Obama’s determined opponent is mooted so often as a running mate that the phrase ‘dream ticket’ is coined over and over. Polling shows the public would welcome an Obama-Clinton ticket, but after Obama spent the last 17 months criticising Clinton as too beholden to the Washington establishment, could he bring her aboard? A bigger question is whether Clinton would accept a vice-presidential offer when she could stay out and be the frontrunner in 2012 if McCain beats Obama Photograph: Robyn Beck/AFP/Getty

James Webb: The Virginia senator is still in his first term, which could add to criticism of Obama’s inexperience. But Webb has a perfect résumé: six Vietnam combat medals, service as navy secretary under Reagan, and his defence of gun ownership. His friendship with John McCain could make the Republican hesitant to attack an Obama-Webb ticket. He is popular with the media, but his fiery candour and well-reviewed but sexually frank novels could be more trouble than Obama can handle Photograph: Karen Bleier/AFP

Ted Strickland: The Ohio governor was an early ally of Hillary Clinton, so his presence would assuage bruised feelings among her supporters. He would boost Democrats’ chances of winning Ohio, a crucial swing state where Obama lost to Clinton in the primaries. The controversy over Obama’s former pastor the Rev Jeremiah Wright is likely to resurface during the fall election battle, which makes Strickland’s noted religious outreach skills all the more attractive Photograph: Tony Dejak/AP

Kathleen Sebelius: Obama often talks about his mother’s Kansas heritage, so picking the state’s affable governor would endear him even more to voters there. Sebelius stayed popular with Kansas conservative voters while opposing a state law to ban gay marriage and vetoing one to protect gun rights. Her reputation for working well with political enemies aligns with Obama’s promise to end vicious partisanship. But a female running mate may have trouble wooing more traditionally minded voters Photograph: Alexa Wong/Getty

Wesley Clark: He is another Clinton ally and would help her supporters feel comfortable with Obama. On military matters he is as formidable as McCain, having spent four years as supreme allied commander of Nato in Europe, and commanding troops in the Balkans conflict. His Arkansas childhood helps him connect with working-class mid-western voters among whom Obama at times struggles. But Clark’s failed run in the 2004 primaries, and lingering criticism of his Nato leadership, could backfire Photograph: Mike Segar/Reuters

John Edwards: The 2004 vice-presidential nominee played down the possibility of a repeat performance when he endorsed Obama last month, but the offer may come the way of the former North Carolina senator anyway. He has strong ties to the working-class Appalachian area where Obama still needs to perform better if he is to win, and his anti-establishment agenda meshes well with Obama’s promise to shake up Washington culture. On the downside, he has reputation for being overly headstrong. Photograph: Sean Gardner/Reuters

Ed Rendell: The gregarious governor of Pennsylvania helped deliver his state for Clinton in April and could do the same for Obama in November. A former district attorney, he would bring military service and a reputation for crime fighting to the ticket, but he is also notorious as a loose cannon. Rendell suggested earlier this year that whites would be reluctant to back Obama because of his race, and mocked his young acolytes for “drinking the Kool-Aid” of his speeches Photograph: Gabriel Bouys/AFP

Bill Richardson: When New Mexico’s governor - and Bill Clinton's former energy secretary - endorsed Obama in March, the tide truly began to turn against Hillary. He offers three key strengths - he has appeal in John McCain’s home region of the American west; he is popular with Hispanic voters, who have yet to fully embrace Obama; and he has stellar foreign policy credentials. Who else can say he has personally helped negotiate North Korea's nuclear disarmament? Photograph: Brendan Smialowski/Getty