Senator Jeffords waved goodbye to the Republican party

He directed the wooing of Senator Jeffords without the Republicans realising it until it was too late.

Mr Daschle is the absolute Senate insider. After leaving the Air Force, where he was in intelligence and obviously learned a trick or two, he worked as a staffer in Congress, became a Congressman and then a Senator.

He will be the new Majority Leader in the Senate.

Other Democrats take over the powerful committee chairs.

• Delaware Senator Joe Biden - who once pinched former British Labour Party leader Neil Kinnock's line about being the first in his family to go to university - has decided to chair the Foreign Relations Committee
• Senator Jeffords's fellow Vermonter Patrick Leahy will head the Judiciary Committee
• Senator Jeffords himself, by the way, gets the Environment Committee
• The rather intellectual Carl Levin takes over on the Armed Services Committee. He is sceptical about Mr Bush's proposed missile defence
• Ted Kennedy will lead the Health Committee, so we can expect the issue to become more prominent.

Shifting alliances

The Senate is still very closely divided and the balance of power could shift again if, for example, someone died and a state governor appointed a successor from the other party.

There are no by-elections for the United States Senate.

Maverick: Senator John McCain could lead a revolt in the Republican Party

The power also shifts to the centre. The moderates, on both sides, will have to be listened to more and more often.

And there are even one or two waverers who could themselves threaten to switch parties just as Senator Jeffords did. It would be a powerful threat.

'Mavericks'

Their own parties do not call these folk moderates. They are called mavericks.

Among them is John McCain, the individualistic former Vietnam prisoner of war who strongly challenged George W Bush during the primaries.

President Bush has tried to be nice to him recently, inviting him to dinner. Senator McCain might not defect to another party but he could lead sections of his own along a different path.

Another Republican waverer is Lincoln Chafee from Rhode Island. He is following his father's footsteps in the Senate. The dad was a liberal Republican. So is the son.

But the Democrats, too, are not totally united. Tom Daschle will have to watch his own back.

Breaking ranks

There is Georgia Senator Zell Miller, a somewhat old school conservative Southern Democrat who broke ranks early to support Mr Bush's tax cuts.

He says he will not switch parties, but he might well switch votes.

One of the key middle of the road Democrats is another Southerner, John Breaux from Louisiana.

George Bush spotted him early as a potential ally and the two had a meeting soon after the election.

Mr Breaux has since been instrumental in forging Democratic support for the President's tax and budget plans.

It is striking how the shift of one Senator can affect so many others.

And all this will change in November of next year when a third of the Senate is up for re-election.