In the three Italian political elections held with the 75%-plurality, mixed-member electoral system, a systematic difference can be observed in vote shares obtained by the two major party coalitions in the plurality versus proportional vote. The article analyses the sources of these differences in the 2001 political elections. Based on precinct data for the whole country, separate analyses are carried out – using the Goodman model – in order to build "turnover tables" between the two arenas for each district of the country. Differentiated behaviours are thus quantified and commented at the national level. An explanatory analysis is then presented, in order to ascertain significant relations between such behaviours and district-level variables such as geographical area, urban setting, number of candidates contesting the district and party affiliation of coalition candidates. The overall result is that differentiated behaviours are dictated both by evaluation of the national competition setting and historical legacy regarding the perception and evaluation of the political space.