Nearly was not close enough to keep Al Gore in the running for the presidency

Al Gore's decision not to run for the US presidency in 2004 was influenced overwhelmingly by one single event: his failure to win it in 2000.

Had he had his way, the former vice-president may well have made a different announcement last night, telling CBS's 60 Minutes that he had decided to make what would have been his third bid for the White House.

After gradually re-entering politics over the past year, Mr Gore had campaigned for selected candidates, made trips to the key states of Iowa and New Hampshire, then spent the past month promoting a book on the family that he wrote with his wife, Tipper.

But while Mr Gore, 54, may have fancied another shot, he was clearly aware that many in the Democratic party did not share that view. Those people had sympathy for Al Gore but they also felt intense anger.

Yes, he was robbed of the presidency the last time, many Democrats would admit. Yes, he won the popular vote. But if he had not conducted such a dull, unconvincing and lacklustre campaign, he would have swept into the White House and the Supreme Court would not have been able to instead hand the jewel to the Republicans. If he had simply managed to win in his home state of Tennessee he would have become President.

Mr Gore admitted that he did not have the wholehearted support of all elements of his party when he announced last night he would not be standing.

"The last campaign was extremely difficult and while I have the energy and drive to go and do it again I think there are a lot of people in the Democratic Party who did not want to," he said. "I personally have the energy and drive and ambition to make another campaign, but I don't think that it's the right thing for me to do."

Mr Gore is also likely to have been influenced by the huge size of the task ahead of him. With the personal approval ratings of President George Bush still running at historically unprecedented levels, he may have thought any effort would be in vain.

The former vice-president's decision not to run in 2004 – he said he had not ruled out running in 2008 or later – will act as the cue for other potential candidates to announce their intention to run. Mr Gore's former running mate, Joseph Lieberman, was last night said to be preparing an imminent statement, his promise not to run if the former vice-president did now having been nullified.

The Massachusetts senator John Kerry – almost certain to run – said: "We all owe Al enormous gratitude for years of dedicated and exemplary public service and for his significant contributions to our party and country."

Also considering the race are the Senate Democratic leader, Tom Daschle, the former party leader in the House, Dick Gephardt, and the North Carolina Senator John Edwards.

The Vermont governor, Howard Dean, who has announced he will run, called called the announcement a "sort of a bittersweet day". He added: "Al Gore must have faced a very difficult decision and he exhibited some real courage in making the decision he did. There is a certain amount of sadness for me because he worked hard in the 2000 election and was poorly served by the process."