When the party was founded, few people took it seriously and many commentators speculated that the ultimate purpose of HSU was to take away pensioners' votes from rejuvenated SDP and thus help ruling HDZ remain in power.

[citation needed] However, the party gradually built its organisation throughout the country and slowly rose in popularity due to both HDZ and left-centre cabinets of Ivica Račan refusing to honour a Constitutional Court verdict that ordered the government to pay back pensions that had been denied in the early 1990s.

[citation needed] At the 2007 Croatian parliamentary election, the party won 101,091 votes and 4.1% of the votes, but this time the electoral math (D'Hondt method) allowed them to receive only a single representative in the Parliament, Silvano Hrelja.

In 2009, the economic crisis caused the government of Jadranka Kosor to start talks about extra crisis taxation and after a row with the finance minister Ivan Šuker, the HSU withdrew their support for the government.

It continued with the coalition Croatia is Growing at the 2015 Croatian parliamentary election.