Here in the US, the rules vary. Some felons are allowed to vote only after rehabilitation and release. Some while they are in jail; some not at all after conviction; some while in office.

In some jurisdictions, they are allowed only to vote for state or local positions.

In some they are counted among the strongest supporters of local politicians.

I believe this is one of the issues the Constitution is mute over and, as such, there are as many answers as there are authorities.