By Imogen Foulkes
BBC correspondent in Berne
Switzerland is set to undergo a political transformation on Wednesday as parliament votes in a new cabinet.
Blocher is well-known for his outspoken views
The right-wing Swiss People's Party is demanding a second seat in cabinet following its success in general elections last October.
Its candidate is Christoph Blocher - famous for his outspoken views on asylum seekers, immigrants and the EU.
The move would change the make-up of Switzerland's four-party coalition for the first time in 44 years.
Mr Blocher has been a key figure in Swiss politics for 20 years, but no one ever really expected to see him in government.
His outspoken opposition to the European Union, and his demands for tough laws on asylum and immigration, do not really fit with Switzerland's traditional consensus style politics.
The same four parties have governed Switzerland since 1959 - two socialist ministers, two radicals, two Christian Democrats, and one Swiss People's Party.
It has been a coalition dominated by the centre right.
But the People's Party has moved even further to the right in recent years and, at the same time, has doubled its share of the vote.
It is now the largest party in parliament, and is legitimately asking for another cabinet seat.
By rights the Christian Democrats, with the least popular support, should give up one of their seats.
But both Christian Democrat ministers have refused, and now parliament must vote.
Campaigning has been feverish and the outcome is uncertain. The Green Party or even the two communist members of parliament could be the deciding factor.
But the People's Party has delivered its ultimatum - elect Christoph Blocher or we leave the government altogether and become the official opposition.
So, whatever happens, the cosy Swiss coalition is at an end.
Inside or outside the cabinet, Christoph Blocher is about to perform the biggest political upset seen in Switzerland in decades.