Welcome to “the Veepstakes” — a game played every four years involving winks, hints and a frenzy of speculation. Participants are required to follow a few red herrings, read their tea leaves and then, as often as not, eat a large portion of humble pie for guessing wrong.

Already the preliminary vetting stage is over, with candidates vying to be Barack Obama’s vice-presidential running-mate having prostrated their private lives and financial dealings in front of an inquisitorial committee based at a Washington law firm.

The winner of a role once compared by Vice-President John Garner to a “bucket of warm p***” may even be announced as soon as this morning.

The New York Times said yesterday that Mr Obama was preparing to announce his choice by sending out millions of text messages and e-mails to supporters — the type of gimmick at which his campaign excels.

Then again, it could be tomorrow or even later before his — or her — identity is known, with The Washington Post detecting signals that Mr Obama may wait until the weekend so that he can maximise publicity before the Democratic convention begins in Denver on Monday.

John McCain, the Republican nominee, is expected to wait until next Friday — his 72nd birthday. It was reported that donors were being asked if they would accept a pro-choice running mate. Then it was said that one such candidate, Tom Ridge, had been ruled out.

The New York Times declared that Mr Obama “has all but settled on his choice” from a shortlist comprising senators Joe Biden and Evan Bayh, as well as the Governor of Virginia Tim Kaine. The next sentence clouded such clarity by saying that many Democrats hoped Hillary Clinton or the Kansas Governor, Kathleen Sebelius, would be picked.

The Washington Post listed the same five names before adding other possibilities including Senator Chris Dodd and New Mexico’s Governor, Bill Richardson, both of whom were forced to drop out of the nomination race at an early stage.

It also mentioned Senator Jack Reed, a military expert, whose Rhode Island home was rumoured yesterday to be “crawling with Secret Service agents”. Even Senator John Kerry, the Democratic nominee four years ago, has been touted as a possible running mate because he has the foreign policy credentials that Mr Obama lacks. So has the former senator Sam Nunn, whom Mr Obama declared would be one of the people he leant upon for advice.

Although Mrs Clinton appeared to have been rejected because of her rivalry with Mr Obama and the tainted past of her husband, Bill, she has become the subject of fresh speculation about a historically charged “unity ticket”.

Polls suggest this is still the preferred option for Democratic voters and she would go some way to balancing Mr Obama’s lack of experience, as well as broadening his appeal to older women or white working-class voters.

Mrs Clinton is steeped in old politics, however, whereas Mr Kaine is what Mr Obama likes to call an “agent of change” who, along with Mr Bayh, might help win a battleground state. The Virginia Governor indicated that he did not expect to get the nod, perhaps because the Georgian crisis had focused minds on foreign affairs.

An unsourced report said that staff had gathered for an emergency meeting to discuss who would take his job “if and when” he is nominated for vice-president. Mr Biden heads most pundits’ shortlists and returned from a fact-finding mission to Georgia on Monday to say how the West must “stand up for the rights of free people throughout the region”.

Yesterday he got a public pat on the back from Mr Obama who promised support for a $1 billion Georgian reconstruction fund proposed by “my friend, Senator Joe Biden”. Later, maybe teasingly, he told reporters camped outside his Delaware home: “I’m not the guy.”

Expect the unexpected. Few predicted that Dick Cheney, asked to find a running-mate for George Bush in 2000, would end up recommending himself. Four years ago the New York Post proclaimed Richard Gephardt to be Mr Kerry’s choice. The next day John Edwards was revealed as the vice-presidential nominee when his name was observed being painted on an aircraft.

So, step forward Bill Nelson, who represents the swing state of Florida in the Senate where he sits on the armed services, foreign relations and intelligence committees. Bloggers typing “Obamanelson.com” discovered that they were redirected to Mr Obama’s official campaign website.

Or perhaps it means his Nebraskan namesake, Senator Ben Nelson, is also in the frame. Bill and Ben — the long shot men.

The chosen ones?

Joe Biden Age 65
Garrulous Senate Foreign Relations Committee chairman

His 1988 White House bid imploded after he was caught plagiarising a Neil Kinnock speech, while this year's attempt ended with 1 per cent support in Iowa. Pros: Good debater who can connect with working class and bolster ticket's foreign policy credentials. Cons: A gaffe-prone Washington veteran insider, he might tarnish promised “new politics” Odds 2/1

Evan Bayh Age 52
Senator and former Governor of Indiana

Good-looking centrist Democrat who was narrowly rejected as running-mate for Al Gore and John Kerry. Pros: Could help Mr Obama to win Indiana, an important battleground state. Cons: A bit wooden in his presentation, while questions have been raised about conflicts of interest with his wife's business career. Odds 3/1

Tim Kaine Age 50
Governor of Virginia

One of the brightest new faces in the Democratic Party, this Spanish-speaking former Jesuit missionary was one of the first to endorse Mr Obama but said recently that he was unlikely to be picked. Pros: Popular Governor in a Southern state that Mr Obama would love to win. Cons: His inexperience, particularly in foreign policy, could reinforce doubts about Obama. Odds 4/1

Kathleen Sebelius Age 60
Governor of Kansas

Socially moderate and popular in her deeply conservative state, her support for Mr Obama helped him to win Kansas this year. Pros: A woman candidate without Hillary Clinton's baggage, she might help to mend fences with angry women voters. Cons: No foreign policy experience and picking her may insult Hillary loyalists. Odds 7/1

Hillary Clinton Age 60
Senator and former First Lady

She had all but been ruled out as running-mate until her name resurfaced this week. Pros: She combines experience with appeal to women and white working-class voters. A surprise choice who would unify the party at a stroke. Cons: She is redolent of “old politics” and has implied that Obama is unfit to be Commander-in-Chief. Also, what role would her husband play - and is there too much dirt on him? Odds 10/1

Odds according to Ladbrokes

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