Index: src/wp-content/themes/twentyfifteen/css/editor-style.css
===================================================================
--- src/wp-content/themes/twentyfifteen/css/editor-style.css	(revision 42426)
+++ src/wp-content/themes/twentyfifteen/css/editor-style.css	(working copy)
@@ -112,6 +112,8 @@
 	padding-left: 17px;
 }
 
+ul > li blockquote,
+ol > li blockquote,
 blockquote > blockquote {
 	margin-left: 0;
 }
Index: src/wp-content/themes/twentyfifteen/style.css
===================================================================
--- src/wp-content/themes/twentyfifteen/style.css	(revision 42426)
+++ src/wp-content/themes/twentyfifteen/style.css	(working copy)
@@ -2728,6 +2728,8 @@
 		margin-left: -1em;
 	}
 
+	ul > li blockquote,
+	ol > li blockquote,
 	blockquote > blockquote {
 		margin-left: 0;
 	}
@@ -2942,6 +2944,11 @@
 		padding-left: 0.85em;
 	}
 
+	ul > li blockquote,
+	ol > li blockquote {
+		margin-left: 0;
+	}
+
 	blockquote p {
 		margin-bottom: 1.75em;
 	}
@@ -4168,6 +4175,11 @@
 		padding-left: 1.1111em;
 	}
 
+	ul > li blockquote,
+	ol > li blockquote {
+		margin-left: 0;
+	}
+
 	blockquote cite,
 	blockquote small {
 		font-size: 15px;
@@ -4846,6 +4858,11 @@
 		padding-left: 0.85em;
 	}
 
+	ul > li blockquote,
+	ol > li blockquote {
+		margin-left: 0;
+	}
+
 	blockquote p {
 		margin-bottom: 1.75em;
 	}