I am disheartened to confirm that as of today, May 26, 2015, MarsEdit will fail to connect to any blogs hosted on Google’s Blogger/Blogspot service.
MarsEdit has supported Blogger for many, many years. A side-effect of having supported it for so long is the app uses an authentication method, ClientLogin, which has been phased out over time, and is no longer supported by Google.
Although I knew that Google was encouraging developers to adopt a newer authentication method, I was not aware that the ClientLogin mechanism would be shut down this month, or even this year.
I am committed to maintaining support for Blogger in MarsEdit, but adapting to a new authentication method is a non-trivial change, and not something I can turn around immediately. I will make it a priority to update MarsEdit as soon as possible, and will post again on this blog when a beta release is ready for testing, so that Blogger users who are anxious to return to MarsEdit can give it a try.
In the mean time unfortunately I don’t know of any workaround that will allow Blogger users to continue using MarsEdit. I appreciate your patience while I work to update the app.