Only one of his 30 backbenchers voted against the motion, which was passed by the large majority of 77 votes to 29. The scene is now set for a showdown on the issue of arms decommissioning, which must be settled before the new administration comes into being.
Among Unionist assembly members the vote was split exactly evenly, at 29-29. While this clearly does not represent a comfortable lead for Mr Trimble, most of his supporters viewed the outcome as at least a relief and at most a victory of sort.
A second backbencher, Roy Beggs Jr, had vacillated on his voting intentions but in the end toed the party line. In doing so he apparently shrugged off the influence of his father, who is an MP and a strong opponent of the Good Friday Agreement.
Mr Beggs Jr said that while he had reservations, he had received concrete assurances on the decommissioning issue from Mr Trimble. He added: "Public opinion across the British Isles is solid on this issue. Unreconstructed terrorists cannot sit in a democratic government."
After the vote the Northern Ireland Secretary, Mo Mowlam, is technically in the position of being able to announce the formation of a new executive. In political terms, however, this must await a new measure of agreement on the decommissioning issue.
This view was endorsed yesterday by the Taoiseach, Bertie Ahern, in the latest of his sometimes confusing statements on decommissioning. He told the Dail in Dublin: "The political reality is that we cannot get to the position of setting up an executive - which we desperately need to do, and we are getting to a situation that is getting more desperate every day - without finding a compromise."
The even 29-29 split among unionist assembly members denied the Rev Ian Paisley the chance to argue that Mr Trimble's stance was supported by only a minority within unionism.
Although the result brought no loss of moral authority for the Ulster Unionist leader, it is plain enough that he kept his supporters on board by assuring them yet again that he could secure actual decommissioning from the IRA, or alternatively could form a new executive without Sinn Fein.
The republican refusal to decommission, on the other hand, remains as implacable as ever, which means a tough period of negotiation lies ahead.
Gerry Adams said last night the transfer of powers to the Assembly would lead to a breakthrough over IRA arms decommissioning. The Sinn Fein president was speaking after a meeting at Downing Street with Tony Blair to keep up the momentum towards the 10 March deadline for transferring powers to the Assembly.
Mr Adams rejected the Unionist demands for decommissioning before sitting in the executive. He said that the transfer of powers would be the key to resolving the impasse.
"My view is that if the two governments keep to the agreement and the parties keep to the agreement, while it will be difficult, this issue can be resolved," he said.Reuse content