Far-right extremism poses the biggest threat to German democracy and voters should bear this in mind before casting their ballot for the nationalist, anti-immigrant Alternative for Germany (AfD) party, the country's domestic spy agency said on Tuesday. The AfD is currently polling at 18-20% nationwide and is on track to win three state votes in eastern Germany with calls to stop migration and curb what it sees as a costly green agenda. Far-right parties have gained ground across Europe but the rise of the AfD touches a particularly sensitive nerve in Germany because of the country's Nazi past. "... parts...