Labour led the SNP in the polls for the 2011 Scottish Parliament election until the campaign began in March, at which point support for the SNP rallied. The SNP went on to win an unprecedented majority in the Scottish Parliament, a result that had been considered impossible under the proportional voting system. Labour had a net loss of 7 seats to the SNP. It also lost most of their constituency seats, although its share of the constituency vote declined by less than 1%. Labour's defeat was attributed to their campaign being directed mostly against the government in Westminster instead of the SNP. Party leader Iain Gray, who held on to his own seat by only 151 votes, announced that he would be resigning with effect from later in the year. Eight weeks later, Labour easily retained a Westminster seat at the Inverclyde by-election. This suggests that Scottish Labour's disappointing performance in the 2011 Scottish Parliament election would not necessarily translate into support for its political opponents in other elections.