Who carries out investigation for election-related criminal offenses?

Switzerland
Article 12. Theprosecution authorities are:
a. the police;
b. the publicprosecutor;
c. theauthorities responsible for prosecuting contraventions.
Article 15. (1) Theactivities of the federal, cantonal and communal police in prosecution mattersare governed by this Code.
(2)The police investigate offences on their own initiative, in responseto reports from members of the public and from authorities, and on theinstructions of the public prosecutor; in doing so, they are subject to thesupervision and the directives of the public prosecutor.
(3) Where criminal proceedings are pending before a court, the court mayissue the police with instructions and assignments.
Article 16 (1) The publicprosecutor is responsible for the uniform exercise of the state's right topunish criminal conduct. (2) It conducts preliminary proceedings, pursuesoffences within the scope of the investigation, and where applicable bringscharges and acts as prosecutor.
Article 17. (1)Authorities responsible for prosecuting contraventions
The Confederation and the cantons may delegate the prosecution andadjudication of contraventions to administrative authorities. (2) Wherecontraventions are committed in connection with a felony or misdemeanour, theyshall be prosecuted by the public prosecutor and judged by the courts at thesame time as the more serious offences.
Swiss Criminal Procedure Code of 5 October 2007 (Status as of 1May 2013)