The conditions that prevailed in 2011 are no more. The 2014 referendum and the ongoing constitutional war of attrition have fundamentally changed the dynamics of how we do politics, of how we think politics. Unionist support is continuing to rally behind the Conservatives, and this, along with the continued success of the SNP in the constituency vote, will now always work against the SNP. Yet, Stewart McDonald is right. The SNP strategy in 2011 has been the only one that has worked, and it has won an SNP majority. It can win that majority again – theoretically, at least.
Conclusion: a single party dominating the Scottish parliament is a mathematical impossibility, it cannot be done. This of course applies, mutatis mutandis, to a single pro-independence party dominating the Scottish parliament so as to stop anything like the 1918 Dáil Éireann election result from happening again; when Sinn Féin took 73 (that is 76.7 percent) of the available 105 Dáil seats. Granted, however, this system was not designed with a view to penalising the SNP in particular.