Insight - In Labour's Scottish bastion, nationalists prepare an upset

By Andy Bruce, Kate Holton and Guy Faulconbridge GLASGOW/LONDON (Reuters) - In Scotland's biggest city, nationalists have triggered a once-in-a-century shift in political loyalties that could dash Labour leader Ed Miliband's dreams of winning the May 7 election and thrust secessionist 'kingmakers' to the heart of British power. The shifting currents in Glasgow, the citadel of Scottish socialism for more than a century, show the seriousness of the nationalists' bid to end