"How do I associate my blogspot blog with a new gmail address? I want to keep the content and change the gmail account." (the answer to this will also be applicable for those who have more than 1 blog but will like different PROFILE for different blogs)
This post is for the old Blogger UI (User Interface) and if you are currently facing problems following the instructions in this post because you are currently using the Blogger new UI, you can revert back to the old Blogger UI, then you will be able to follow the instructions in this old post.
If you want to use a different email address, whether gmail or other email address, to access Blogger, all you have to do is to sign into Dashboard and click SETTINGS > PERMISSION and add yourself with the new email address as an author.

Now for convenience, it is best you open another browser (see why I have so many browsers in my computer) without signing out of Blogger. Sign into your new email address and you should see a message from Blogger which should be the one containing the invitation. Accept the invitation.
Update: From a commentator: " I tried adding my yahoo email and I made it an admin but I couldn't log in. So, I created another gmail account and viola! It worked"
My response: Actually, any email address will do, not only gmail. Only thing is, that email should have associated with it a Blogger/Google account, and if it doesn't, it is easy to create one for the purpose of becoming an author/administrator
My response: Actually, any email address will do, not only gmail. Only thing is, that email should have associated with it a Blogger/Google account, and if it doesn't, it is easy to create one for the purpose of becoming an author/administrator
Now go back to your Blogger account in the other browser where you are still logged in and in the PERMISSION tab. You should see your other email address added as an author. Give yourself admin rights. Now if you are sure that you have added yourself with the new email address (I suggest you double check), you may remove yourself with the old email address if you wish.
Update: For those having problems, I hope this comment by Anne can help you:
. For those with multiple emails, gmails, Blogger accounts etc. and currently faces the irritation of having to continually sign in and sign out, read my recommendation on how to easily overcome that below.I originally had the same problem as some other people. I had my blog with my ABC gmail account but wanted to switch it to my DEF gmail account. Every time I tried the instructions, it still wouldn't let me sign in with my DEF gmail account. I realized my problem: going to Dashboard, then Edit User Profile, then "Email address," I had updated that section to my DEF email. However, once I switched that section back to the ABC email and then went through your instructions, it worked perfectly and I could use the DEF gmail! Not sure if that's helpful for others with the same problem!
If you have multiple accounts and currently is irritated by having to repetitive sign in and sign out, my suggestion is to use more than one browser as different browsers have different browser cache, meaning you can be logged in Account 1 with, say, Firefox while at the same time also logged into Account 2 with, say, Google Chrome and instead of repetitively logging in and logging out, you just switch from browser to browser with no need to log out in any of your browsers.