Party Competition and Signalling to Regional Constituencies: Evidence from Co-Sponsorship Networks in Portugal

Portugal's closed list proportional electoral system makes parties dominant players in the determination of candidates. The parties face a trade-off between maintaining party unity and gaining votes by allowing regional candidates to defect from the party line. We analyze this trade-off using co-sponsorship networks from 1986-2016. We use spatial lags to determine how regional a proposal is. We show that, close to elections, government parties allow more regional initiatives from districts where they did poorly in the last election. Opposition parties are more likely to allow regional initiatives as a signal to voters in their strongholds.