Holger K. Nielsen became one of the leaders in this campaign,[2] and was later judged to have swung far more than his own socialist voters towards the NO-side, which to great surprise emerged victorious by a wafer-thin margin.

During this time the party entered into several major compromises with the government in many policy areas, including several state finance bills.

However close the socialists moved to the government, though, they never quite became acceptable as coalition partners, much to the chagrin of Holger K. Nielsen.

The party remained in the sceptic camp during the 1998 referendum campaign for the Amsterdam Treaty, a move which prompted several prominent pro-Europeans, such as Steen Gade and Christine Antorini, to leave politics.

Again in 2000, when the issue was Denmark entering the Economic and Monetary Union, the Socialists were in the forefront of the successful NO-campaign, with Holger K. Nielsen taking a prominent lead.

However later that same year, riding high in the opinion polls, Holger K. Nielsen performed a spectacular U-turn and made his party endorse the Nice Treaty, thus making a referendum avoidable.