In the 2003 federal election, they had a joint slate with the Free Democratic Party. They are very much the junior partner, with only 2.2% of the vote compared with the FDP's 17.3%. However, in their strongholds, in the Protestant cantons of Romandy and the canton of Basel-City, they did better. Their best performance was in Geneva, where they received 16.8% of the vote. It won 4 seats (out of 200) in the Swiss National Council, but was represented in neither the second chamber nor in the Swiss Federal Council. After the election, the LPS and FDP founded a common group in the Federal Assembly. In June 2005, they strengthened their cooperation by founding Radical and Liberal Union
By 2005, it held 3.7% of the seats in the Swiss Cantonal parliaments, 2.9% of the Cantonal government seats (BADAC index, weighted by population and number of seats). At the last election, on 22 October 2007, the party won 1.8% of the popular vote and 4 out of 200 seats.