Secrecy surrounds Obama's choice of perfect running mate

Barack Obama resumed coast-to-coast campaigning yesterday as he approached what could prove the most critical juncture of his long campaign for president – the choice of the perfect running mate ahead of Monday's start of the Democratic Convention.

The shroud of secrecy around the process remains as impenetrable as ever, although rumours abound. By stopping in New Mexico, he reignited murmurs about the state's Governor, Bill Richardson (Hispanic by birth), considered a long-shot possibility. Tomorrow, he will be in Virginia with Governor Tim Kaine, persistently fancied in whispers.

At the weekend there was the praise Mr Obama lavished on former Georgia Senator Sam Nunn. An ex-chairman of the Armed Services Committee, Nunn is old at 69, but would plug holes in Obama's résumé – foreign relations and defence.

Only the tightest circle of Mr Obama's advisors in Chicago have a clue to what he is thinking. But those on the final shortlists are likely to know it, if only because of the intense vetting that must be completed before an announcement is made. Thus the answers they give to enquiries on the subject are gauged with intense care. Kathleen Sebelius, the Governor of Kansas, denied she was under consideration then stopped denying it. She is too coy not to be in play. Indiana Senator Evan Bayh, seen by some as Veep-stakes favourite, partly because of his popularity in a swing state, has tight lips too.

Obama's decision will be disseminated instantly by text message. This is more than a gimmick. Voters were invited last week to text campaign HQ and ask to be among the first to learn of the Veep choice. Thus the campaign hopes to reap a huge harvest of cell phone numbers for its get-out-the-vote drive in November.

If not Nunn, there is another foreign affairs veteran mentioned as an Obama second wheel – Senator Joe Biden of Delaware, who did himself no harm by heading to Georgia for talks with President Saakashvili in Georgia at the weekend.

Mr Obama told a group at a fundraiser in San Francisco on Sunday: "I will win, don't worry about that."

He presumably knows something we don't. Including the identity of the man or woman he wants by him for the rest of the campaign.