The national vote is split in half, the socialist or left wing parties do not have a majority. The PvdA can only rule Dutch politics by joining with the centrist Christian Democrats in a new coalition. The election campaign will not be about substance, rather which of the three parties will be the largest and deliver the initiative of coalition talks and the new Prime Minister. The largest parties will pull voters away from all other minority parties. The government decision making process will be on hold for all of this year until a new cabinet is installed. This may be a heavy burden for the PvdA to carry during the worst economic recession for decades. Job Cohen has no record for financial policy, however in a quick poll he was by far favorite by all voters to become the new Prime Minister. Mission accomplished.
"But I will not let myself be reduced to silence."
I suspect it was simlpy a cummulative build-up, aided by the pressure of regional elections, and Bos drew the line in the sand with Uruzgan.
Possibly his stance was psychologically strengthened by knowing in advance that you've plans to step down and already have a successor arranged.
With Cohen in, the national elections are now quickly becoming reduced to three parties, all striving to become the largest: CDA, PvdA, Wilders. Potentially to the loss of votes for D66, VVD, SP and Green Left.