Index: src/wp-content/themes/twentytwelve/css/editor-blocks.css
===================================================================
--- src/wp-content/themes/twentytwelve/css/editor-blocks.css	(revision 58054)
+++ src/wp-content/themes/twentytwelve/css/editor-blocks.css	(working copy)
@@ -289,10 +289,6 @@
 	font-style: italic;
 }
 
-.edit-post-visual-editor .wp-block-pullquote {
-	margin: 0;
-}
-
 .wp-block-pullquote .wp-block-pullquote__citation,
 .wp-block-pullquote cite {
 	font-size: 14px;