DUBLIN — Irish voters have decisively approved a 27-nation treaty that would reshape European Union institutions to make them more effective after a decade of eastward expansion, according to political leaders, analysts and partial results Saturday.

Electoral officials said "yes" votes were outnumbering "no" in 41 of Ireland's 43 constituencies, a total reversal from the country's stunning rejection of the Lisbon Treaty last year.

The Irish agreed to vote again Friday after EU leaders offered key assurances designed to undermine anti-treaty arguments. The EU dropped its plans to prune the size of the European Commission, a move that would have cost Ireland its right to hold a seat continuously on the EU's key executive body. Brussels also reiterated that it would have no control over Ireland's taxes, military neutrality or moral codes.

The treaty reached by national leaders in the Portuguese capital in 2007 spells out how the EU should reshape its decision-making, size and image in line with its growth into Eastern Europe. It proposes to increase the ability of leaders to make decisions with majority rather than unanimous votes, but also gives more influence in policy-shaping to national legislatures and the European Parliament.

The agreement requires unanimous ratification across the 27-nation bloc, and the Irish are the only ones who required its approval by popular vote. All the other EU nations already have passed the treaty through their parliaments.