Make user as Default contributor for all Blog Posts

It sounds like you want to change the Author for existing posts.

If this is the case, in your Admin screen, go to

Posts | All Posts

and place a checkmark next to whichever posts you want to reassign the Author. Then, near the top, in the Bulk Actions dropdown, select Edit and click Apply. You’ll see something similar to the image below. Select the appropriate Author from the dropdown shown.

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