WHO'S IN THE RUNNING: Denis Stauntonreports.
DEMOCRATS
Hillary ClintonNew York senator, former first lady and defeated candidate. PROSWon 18 million primary votes, reaches groups Obama needs, especially women, Hispanics and older voters. Could help to unite Democrats. CONSUndermines message of change, criticised Obama harshly in primaries, brings her husband's political baggage as well as her own. Could help to unite Republicans.
Ted StricklandGovernor of Ohio, former congressman. PROSAn ordained Methodist minister with a record of support for gun rights - could reassure conservative Democrats and deliver his own state. CONSNo national-security experience, only governor 18 months. Once described Obama as "fluff".
Jim WebbFirst-term senator from Virginia, former Navy secretary under Ronald Reagan. PROSA Vietnam veteran, offers national-security credentials and appeals to conservative, rural voters. Could help to deliver Virginia. CONSNot a team player; leaves senate seat open as Democrats hope to pick up second seat in Virginia; controversy over alleged sexism; wrote dubious novels.
Sam NunnFormer Georgia senator and armed-services committee chairman PROSAdds gravitas and experience; gold-plated national-security credentials; could help win southern states. CONSToo conservative on gay rights and women's issues for many Democrats.
REPUBLICANS
Mitt RomneyFormer Massachusetts governor and defeated rival. PROSA successful businessman, offers the economic expertise McCain lacks. Could help to win Michigan and boost support in Nevada and Massachusetts. CONSRecord of bitter exchanges with McCain in primaries; could face prejudice over Mormon faith.
Tim PawlentyMinnesota governor. PROSYoung leader of a Midwestern swing state, popular among both fiscal and social conservatives. CONSRelatively unknown; recently in trouble for joking that he doesn't have sex with his wife.
Bobby JindalLouisiana governor, former congressman. PROSSon of Indian immigrants, adds youthful diversity to Republican ticket but popular with party base. CONSToo inexperienced; too conservative on social issues to woo independents; Louisiana is already safe for McCain.
Rob PortmanFormer Ohio congressman, director of Office of Management and Budget and US Trade Representative. PROSBrings economic expertise; moderate policy outlook; could help win Ohio. CONSToo dull, associated with unpopular trade policy.