If Sinn Fein emerges with the most seats in the Northern Ireland Assembly elections this week, it will not be because the party has grown in popularity since the last vote in 2017. It will be because support for the DUP is at its lowest in more than two decades. The DUP has suffered because of its failure to prevent Boris Johnson from agreeing the protocol that left Northern Ireland subject to EU single-market and customs rules. Sinn Fein, meanwhile, has benefited from Brexit and the Conservatives’ assertion of a muscular form of Unionism, both of which have added legitimacy to calls for a border poll on Irish unity. Another, more overlooked reason for Sinn Fein’s relative buoyancy is that it has retained the support of younger voters despite being part of government for most of the time since 2007.