"Merkel stop watching us" screamed a banner above a noisy group of protesters which forced Angela Merkel to raise her voice as she launched her election campaign. Barely concealing her irritation, the German chancellor struggled to drown out honking vuvuzelas, and chants of "hypocrite" and "liar", with promises of more of the same from a third term at the helm of Europe's biggest economy - jobs, stability and stronger growth.