diff --git includes/ajax.inc includes/ajax.inc
index 74b4e73..84dc14e 100644
--- includes/ajax.inc
+++ includes/ajax.inc
@@ -193,11 +193,24 @@
  *   functions.
  */
 function ajax_render($commands = array()) {
+  // Update the page state and determine the new CSS and JavaScript that needs
+  // to be loaded. If there is no prior page state, something is wrong.
+  drupal_static_reset('drupal_page_state_id');
+  if ($prior_page_state = drupal_get_page_state()) {
+    $new_page_state = $prior_page_state;
+    drupal_update_page_state($new_page_state);
+    $new_css = array_diff_key($new_page_state['css'], $prior_page_state['css']);
+    $new_js = array_diff_key($new_page_state['js'], $prior_page_state['js']);
+    unset($new_js['settings']);
+  }
+
   // Automatically extract any 'settings' added via drupal_add_js() and make
   // them the first command.
   $scripts = drupal_add_js(NULL, NULL);
   if (!empty($scripts['settings'])) {
     array_unshift($commands, ajax_command_settings(call_user_func_array('array_merge_recursive', $scripts['settings']['data'])));
+    $commands[0]['styles'] = isset($new_css) ? drupal_get_css($new_css) : '';
+    $commands[0]['scripts'] = isset($new_js) ? drupal_get_js('header', $new_js) : '';
   }
 
   // Allow modules to alter any AJAX response.
@@ -526,6 +539,7 @@ function ajax_process_form($element, &$form_state) {
 
     $form_state['cache'] = TRUE;
   }
+  drupal_page_state_enabled(TRUE);
   return $element;
 }
 
diff --git includes/common.inc includes/common.inc
index 14e716b..1762f16 100644
--- includes/common.inc
+++ includes/common.inc
@@ -6794,3 +6794,79 @@ function drupal_get_updaters() {
   }
   return $updaters;
 }
+
+/**
+ *
+ */
+function drupal_page_state_id($new_id = NULL) {
+  $id = &drupal_static(__FUNCTION__);
+  if (isset($new_id)) {
+    $id = $new_id;
+  }
+  // Security care must always be taken when using raw $_POST data.
+  elseif (!isset($id) && isset($_POST['_page_state_id']) && is_string($_POST['_page_state_id']) && preg_match('/^[0-9a-f]{32}$/', $_POST['_page_state_id'])) {
+    $id = $_POST['_page_state_id'];
+  }
+  return $id;
+}
+
+/**
+ *
+ */
+function drupal_get_page_state($id = NULL) {
+  if (!isset($id)) {
+    $id = drupal_page_state_id();
+  }
+  if ($id && $cached = cache_get('page_state_' . $id, 'cache_form')) {
+    $page_state = $cached->data;
+  }
+  else {
+    $page_state = array();
+  }
+  return $page_state;
+}
+
+/**
+ *
+ */
+function drupal_page_state_enabled($enable = NULL) {
+  $enabled = &drupal_static(__FUNCTION__);
+  if (isset($enable)) {
+    $enabled = $enable;
+  }
+  elseif (!isset($enabled)) {
+    $enabled = (bool) drupal_page_state_id();
+  }
+  return $enabled;
+}
+
+/**
+ *
+ */
+function drupal_update_page_state(&$page_state = NULL) {
+  if (!isset($page_state)) {
+    $page_state = drupal_get_page_state();
+  }
+  foreach (module_implements('page_state_update') as $module) {
+    $function = $module . '_page_state_update';
+    $function($page_state);
+  }
+
+  // There can be many users viewing pages that need their page state persisted.
+  // We don't want each one having a randomly generated id, as that would flood
+  // the cache bin with many records. By basing the id on the page state
+  // content, we only need as many records as there are unique states.
+  $page_state_id = drupal_hash_base64(serialize($page_state));
+
+  // $page_state serves a similar purpose to $form_state. Therefore, persist it
+  // in the same cache bin with the same 6 hour life time.
+  cache_set('page_state_' . $page_state_id, $page_state, 'cache_form', REQUEST_TIME + 21600);
+
+  // The browser will need to know the new page state id.
+  drupal_add_js(array('pageStateId' => $page_state_id), 'setting');
+
+  // Future calls to drupal_page_state_id() during this page request should
+  // retrieve the new id.
+  drupal_page_state_id($page_state_id);
+  return $page_state_id;
+}
diff --git includes/theme.inc includes/theme.inc
index ecbded1..b69f7cf 100644
--- includes/theme.inc
+++ includes/theme.inc
@@ -2443,6 +2443,13 @@ function template_process_maintenance_page(&$variables) {
   $variables['head']    = drupal_get_html_head();
   $variables['css']     = drupal_add_css();
   $variables['styles']  = drupal_get_css();
+
+  // If necessary, persist page state information to enable AJAX functionality.
+  // This updates a JavaScript variable, so do this before calling
+  // drupal_get_js().
+  if (drupal_page_state_enabled()) {
+    drupal_update_page_state();
+  }
   $variables['scripts'] = drupal_get_js();
 }
 
diff --git misc/ajax.js misc/ajax.js
index 553d2cc..5413288 100644
--- misc/ajax.js
+++ misc/ajax.js
@@ -206,6 +206,9 @@ Drupal.ajax.prototype.beforeSubmit = function (form_values, element, options) {
   // Disable the element that received the change.
   $(this.element).addClass('progress-disabled').attr('disabled', true);
 
+  // Give the server information about the page state.
+  form_values.push({ name: '_page_state_id', value: Drupal.settings.pageStateId });
+
   // Prevent duplicate HTML ids in the returned markup.
   // @see drupal_html_id()
   $('[id]').each(function () {
@@ -418,6 +421,12 @@ Drupal.ajax.prototype.commands = {
    * Command to set the settings that will be used for other commands in this response.
    */
   settings: function (ajax, response, status) {
+    if (response.styles) {
+      $('head').append(response.styles);
+    }
+    if (response.scripts) {
+      $('head').append(response.scripts);
+    }
     if (response.merge) {
       $.extend(true, Drupal.settings, response.settings);
     }
diff --git modules/system/system.module modules/system/system.module
index e46aa5c..2eb62bd 100644
--- modules/system/system.module
+++ modules/system/system.module
@@ -3684,3 +3684,15 @@ function system_admin_paths() {
   );
   return $paths;
 }
+
+/**
+ * Implements hook_page_state_update().
+ */
+function system_page_state_update(&$page_state) {
+  $page_state += array(
+    'css' => array(),
+    'js' => array(),
+  );
+  $page_state['css'] = array_merge($page_state['css'], drupal_add_css());
+  $page_state['js'] = array_merge($page_state['js'], drupal_add_js());
+}