London — The leader of Britain's opposition Labour Party, James Callaghan, has resigned, and contenders are already throwing their hats into the political ring.
It promises to be the most fiercely fought Labour leadership contest in years , although the shadow Chancellor of the Exchequer, Denis Healey, is given an edge over hsi rivals at this stage.
The former prime miniters's decision not to seek reelection as leader comes at a time when the Labour Party is deeply split between its left and moderate wings.
After days of doubt, Mr. Callaghan announced that he would best serve the Labour movement by going now.
Party left-wingers, headed by Tony Benn, wanted him to continue long enough to let the party decide new leadership election rules. But since new rules would probably favor the party's radical wing, the moderates wanted Mr. Callaghan to bow out quickly so that his successor could be elected on the existing rules.
Their calculation is that whoever is chosen simply on the votes of Labour members of Parliament (the present system) will be well placed to win a later ballot, in which the views of the trade unions and constituency parties are to be strongly represented.
That is not a formula Mr. Benn is willing to approve. Although he made a big impact at the Labour Party conference in Blackpool last month, moving party policy sharply to the left, Mr. Benn and his followers were unable to push through a motion requiring leadership elections to be done by an electoral college.
If they had succeeded, Mr. Healey's chances of becoming leader would be much lower than they are. Mr. Benn might have been within reach of the leadership. At present, however, he may not be able to command the support of more than 20 percent of Labour MPs, according to some estimates.
Instead, Mr. Healey is expected to draw strong support from the right and center of the party. Somewhat to his left is the shadow foreign affairs spokesman, Peter Shore. Another possibility is the party's deputy leader, Michael Foot, a former left-winger who has moderated his ideas in the last few years. Still another contender is John Silkin, a former minister of agriculture.
Assessments of Mr. Callaghan's leadership are sharply conflicting. Some see him as a man of reconciliation who was unable at the end to cope with challenges from left-wing ideologues marching under Mr. Benn's banner.
Others accuse him of losing the 1979 general election unnecessarily and bringing Margaret Thatcher's Conservative Party to power.
Many, however, feel that it was simply time for Mr. Callaghan to go anyway, if Labour wants to heal its divisions and begin shaping up to the Tories.
Mr. Callaghan, announcing his departure, made this point himself. It is widely assumed that the wants Mr. Healey to become leader, feeling he has the intelligence and toughness to carry a future electoral college with him.
An opinion poll on the eve of Mr. Callaghan's decision to resign showed Labour voters giving Mr. Healey 29 percent support, Mr. Benn 26 percent, and Mr. Shore 5 percent.
Despite apparently adverse popular reaction to the public bickering at the party's Blackpool conference, the same poll showed Labour eight points ahead of the Tories were the election were to be held now.
Westminster insiders say Mr. Healey has little hope of persuading left-wing groups in the constituencies that he would make a better leader than Mr. Benn.