What happened
Agenda 2010, announced by Schröder to the Bundestag in March 2003, restructured German unemployment support. The Hartz IV reforms in particular merged long-term unemployment assistance with social welfare at a lower rate than the previous unemployment benefit, and tightened requirements to accept available work.
The reforms are widely credited by mainstream economists with restoring German competitiveness after a period dubbed 'the sick man of Europe' — wage restraint and labour flexibility helped drive the export boom of the 2010s. But the political cost fell heavily on the SPD's own coalition of industrial and working-class voters, many of whom experienced Hartz IV as a punitive, humiliating system of benefit sanctions.
A faction of the SPD's left broke away to help found what became Die Linke. More consequentially for the subject of this timeline, a significant bloc of working-class voters who felt abandoned by the SPD did not return to it — many drifted over the following decade toward parties, ultimately including the AfD, that promised to represent people the mainstream had supposedly forgotten.