Yes, there are policies about this.
The General Handbook issued to church members and leaders has direct language on the subject in section 20, section 35, and section 38, with 38 being the most relevant for this question.
To summarize them, church property can be used for voter registration or for polling, under certain conditions. Church property cannot be used for fundraising, campaigning, endorsing, rallies, or any other political process. Church records, such as lists of addresses, cannot be used for political purposes. The church does not endorse political parties, candidates, or platforms.
The church does sometimes back specific legislation, though this can only be done under the direction of the First Presidency.
No leader at any level should be giving political statements during church meetings or activities. In this case, "political statements" needs to be defined. The church has a number of issues it considers moral in nature, which it has official stances on and which leaders can discuss, and some of these can be considered political. Abortion is one such topic, which may be considered a political issue but which the church considers a moral issue. Even here, however, leaders should not be discussing which candidates are for or against abortion, what parties or platforms think about abortion, how members should vote in regards to abortion, etc.
Leaders can, and are encouraged, to be politically active outside of their church duties. This means they absolutely can make political statements anytime and anywhere that is not an official church event (ie sponsored activities and meetings), including in the homes of members, in a park, in a store, in a PTA meeting, etc.
Under these conditions, the handbook specifies they should not use their status as an ecclesiastical leader to influence how people vote, and they should not ever claim their opinions are representative of the church or its other leaders.
Interestingly, missionaries are told not to discuss politics at all, using very different language than what is used to instruct bishops and other members.
As has been noted in other answers and comments, bishops are not perfect. I've personally heard bishops make political statements in meetings, though they usually apologize and retract the statement as inappropriate. I understand that even if an apology is given, one can still be influenced by such statements.
Covid and responses to it have become highly politicized and sensitive issues. It is just one example where it can be hard to say what is "political" or "not political", even if no political party/candidate/platform is mentioned. Again, bishops aren't perfect, and some of their opinions will leak out from time to time; such should be addressed with the bishop even if the statement in question is "merely" offensive and not political at all.
Without context for the event in question, I cannot say what you should or should not do (or have done). If the bishop is going against church policies, it should be addressed as any other mistake should be: calmly, directly, and without guile. If the bishop continues to go against church policies, it should absolutely be brought up with the stake president, who will counsel with the bishop to stop his behavior, or possibly explain why the bishop's actions were not in disagreement with church policy. Should a stake president be at fault, there are other authorities to go to.