Index: src/wp-includes/js/tinymce/plugins/wordpress/plugin.js
===================================================================
--- src/wp-includes/js/tinymce/plugins/wordpress/plugin.js	(revision 28444)
+++ src/wp-includes/js/tinymce/plugins/wordpress/plugin.js	(working copy)
@@ -348,13 +348,20 @@
 		}
 
 		// Keep empty paragraphs :(
-		e.content = e.content.replace( /<p>(<br ?\/?>|\u00a0|\uFEFF)?<\/p>/g, '<p>&nbsp;</p>' );
+		e.content = e.content.replace( /<p>(?:<br ?\/?>|\ufeff|\s)+?<\/p>/g, '<p>&nbsp;</p>' );
 
 		if ( editor.getParam( 'wpautop', true ) && typeof window.switchEditors !== 'undefined' ) {
 			e.content = window.switchEditors.pre_wpautop( e.content );
 		}
 	});
 
+	// Remove spaces from empty paragraphs.
+	editor.on( 'BeforeSetContent', function( event ) {
+		if ( event.content ) {
+			event.content = event.content.replace( /<p>(?:&nbsp;|\ufeff|\s)+<\/p>/gi, '<p></p>' );
+		}
+	});
+
 	editor.on( 'preInit', function() {
 		// Don't replace <i> with <em> and <b> with <strong> and don't remove them when empty
 		editor.schema.addValidElements( '@[id|accesskey|class|dir|lang|style|tabindex|title|contenteditable|draggable|dropzone|hidden|spellcheck|translate],i,b' );