The erosion of trust in political parties may have contributed to these trends. Although there are long-standing debates on whether political support stimulates or discourages participation in elections (Dalton 2004: ch.8; Norris 1999), the impact of trust in parties seems more predictable.
Individuals who distrust the reliability of parties and the system of party
government have less incentive to become active in a campaign structured
around party politics. In contrast, citizens who trust parties presumably want
their party to win at the next election and participate to achieve this end.