It has also been claimed monarchism and republicanism in Australia delineate historical and persistent sectarian tensions with, broadly speaking, Catholics more likely to be republicans and Protestants more likely to be monarchists. This developed out of a historical cleavage in 19th- and 20th-century Australia, in which republicans were predominantly of Irish Catholic background and loyalists were predominantly of British Protestant background. Whilst mass immigration since the Second World War has diluted this conflict, the Catholic–Protestant divide has been cited as a dynamic in the republic debate, particularly in relation to the referendum campaign in 1999. Nonetheless, others have stated that Catholic–Protestant tensions—at least in the sense of an Irish–British conflict—are at least forty years dead.