My old Google account was overtaken by spam, and so I'm transitioning to a new Google account.
Is there a way to migrate my Stack Overflow identity to the new Google ID?
In your user profile, close to "edit," there is the "add openid" link; using that link you can add another OpenID account (in your case, the new Google account). If you have already defined two OpenID accounts, the link I reported becomes "change openid;" using that link you change the alternative account you already defined.
You can also swap the main OpenID account, and the alternate account.
This thread is way too old. But, now we can add more accounts. Its quite visible
I was searching of the same and came across this post. So sharing if someone else search for it