Dominique de Buman from canton Fribourg has become the first centre-right Christian Democrat Party candidate to compete for a cabinet seat.
The party vice-president is the fifth candidate to join the race to replace outgoing Interior Minister Pascal Couchepin in November. De Buman's announcement has caused surprise among his party and observers.
The 53-year-old French-speaker has been a member of parliament since 2003. He was also mayor of Fribourg from 1994 to 2004.
De Buman told Party President Christophe Darbellay on Thursday night that he planned to join the race in response to a request for candidates by the Christian Democrat electoral commission. De Buman had not been mentioned in the past as a possible cabinet contender, unlike Darbellay.
"I have 23 years' political experience... my political line is that of consensus and national cohesion to try to be a bridge-builder," de Buman told public radio on Friday.
Darbellay said de Buman's candidacy was not part of the Christian Democrat planned scenario but was valid and understandable.
So far four other politicians from the French-speaking part of the country have been named: Pascal Broulis, Martine Brunschwig Graf, Christian Lüscher and Didier Burkhalter - all from the centre-right Radical Party. But more candidates, including from other parties, could emerge ahead of the vote by both chambers of parliament on September 16.
The seven-strong cabinet is made up of two members from the Radicals and two from the centre-left Social Democrats, as well as one from the rightwing Swiss People's Party, one from the Christian Democrats and one from the centre-right Conservative Democrats.
swissinfo.ch and agencies
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