Do Catholics actually vote for Alliance? I thought Alliance was basically an all-Protestant (albeit not politically Protestant) party.
The Northern Ireland Life and Times survey in 2010 suggested that for those who declared their support for the Alliance Party in 2010, 35% were Protestant, 19% Catholic and 46% had no religion. After Sinn Fein and the SDLP, the Alliance got the most votes from Catholics, though only about 8% said they supported the party. Given Irelands STV electoral system, they probably get a significant but not a huge number of lower preference votes or tactical votes from Catholics. This is probably greater in areas where the Catholic community is particularly small enough that the Nationalist parties either don't field candidates or simply field paper candidates.
In North Down constituency for example, 12% are of a 'Catholic community background.' In 2011, the SDLP and SF combined votes in the first round for North Down was 3.7%. The Alliance got 11%. In the local elections for the North Down Council, where the Catholic community is 13%, the Nationalist vote was 1.2%. Unless Catholics by a 11-1 margin simply don't vote, then a high proportion of them probably voted for the Alliance or the case of the local elections parties such as the Greens.
