diff --git a/django/contrib/admin/forms.py b/django/contrib/admin/forms.py
index 6814fc9083..05788d9cb1 100644
--- a/django/contrib/admin/forms.py
+++ b/django/contrib/admin/forms.py
@@ -4,30 +4,23 @@ from django import forms
 
 from django.contrib.auth import authenticate
 from django.contrib.auth.forms import AuthenticationForm
-from django.utils.translation import ugettext_lazy
-
-ERROR_MESSAGE = ugettext_lazy("Please enter the correct %(username)s and password "
-        "for a staff account. Note that both fields may be case-sensitive.")
+from django.utils.translation import ugettext_lazy as _
 
 
 class AdminAuthenticationForm(AuthenticationForm):
     """
     A custom authentication form used in the admin app.
-
     """
-    this_is_the_login_form = forms.BooleanField(widget=forms.HiddenInput, initial=1,
-        error_messages={'required': ugettext_lazy("Please log in again, because your session has expired.")})
+    error_messages = {
+        'invalid_login': _("Please enter the correct %(username)s and password "
+                           "for a staff account. Note that both fields may be "
+                           "case-sensitive."),
+    }
 
-    def clean(self):
-        username = self.cleaned_data.get('username')
-        password = self.cleaned_data.get('password')
-        message = ERROR_MESSAGE
-        params = {'username': self.username_field.verbose_name}
-
-        if username and password:
-            self.user_cache = authenticate(username=username, password=password)
-            if self.user_cache is None:
-                raise forms.ValidationError(message, code='invalid', params=params)
-            elif not self.user_cache.is_active or not self.user_cache.is_staff:
-                raise forms.ValidationError(message, code='invalid', params=params)
-        return self.cleaned_data
+    def confirm_login_allowed(self, user):
+        if not user.is_active or not user.is_staff:
+            raise forms.ValidationError(
+                self.error_messages['invalid_login'],
+                code='invalid_login',
+                params={'username': self.username_field.verbose_name}
+            )
diff --git a/django/contrib/admin/sites.py b/django/contrib/admin/sites.py
index 3d12b25d36..b83c2e3203 100644
--- a/django/contrib/admin/sites.py
+++ b/django/contrib/admin/sites.py
@@ -15,8 +15,6 @@ from django.utils.translation import ugettext_lazy, ugettext as _
 from django.views.decorators.cache import never_cache
 from django.conf import settings
 
-LOGIN_FORM_KEY = 'this_is_the_login_form'
-
 
 class AlreadyRegistered(Exception):
     pass
@@ -193,8 +191,6 @@ class AdminSite(object):
         cacheable=True.
         """
         def inner(request, *args, **kwargs):
-            if LOGIN_FORM_KEY in request.POST and request.user.is_authenticated():
-                auth_logout(request)
             if not self.has_permission(request):
                 if request.path == reverse('admin:logout', current_app=self.name):
                     index_path = reverse('admin:index', current_app=self.name)
diff --git a/django/contrib/admin/templates/admin/login.html b/django/contrib/admin/templates/admin/login.html
index 1371514d43..1c8ae35c35 100644
--- a/django/contrib/admin/templates/admin/login.html
+++ b/django/contrib/admin/templates/admin/login.html
@@ -12,14 +12,14 @@
 {% block breadcrumbs %}{% endblock %}
 
 {% block content %}
-{% if form.errors and not form.non_field_errors and not form.this_is_the_login_form.errors %}
+{% if form.errors and not form.non_field_errors %}
 <p class="errornote">
 {% if form.errors.items|length == 1 %}{% trans "Please correct the error below." %}{% else %}{% trans "Please correct the errors below." %}{% endif %}
 </p>
 {% endif %}
 
-{% if form.non_field_errors or form.this_is_the_login_form.errors %}
-{% for error in form.non_field_errors|add:form.this_is_the_login_form.errors %}
+{% if form.non_field_errors %}
+{% for error in form.non_field_errors %}
 <p class="errornote">
     {{ error }}
 </p>
@@ -29,13 +29,12 @@
 <div id="content-main">
 <form action="{{ app_path }}" method="post" id="login-form">{% csrf_token %}
   <div class="form-row">
-    {% if not form.this_is_the_login_form.errors %}{{ form.username.errors }}{% endif %}
+    {{ form.username.errors }}
     <label for="id_username" class="required">{{ form.username.label }}:</label> {{ form.username }}
   </div>
   <div class="form-row">
-    {% if not form.this_is_the_login_form.errors %}{{ form.password.errors }}{% endif %}
+    {{ form.password.errors }}
     <label for="id_password" class="required">{% trans 'Password:' %}</label> {{ form.password }}
-    <input type="hidden" name="this_is_the_login_form" value="1" />
     <input type="hidden" name="next" value="{{ next }}" />
   </div>
   {% url 'admin_password_reset' as password_reset_url %}
diff --git a/docs/releases/1.7.txt b/docs/releases/1.7.txt
index c79841eb4b..41ad106232 100644
--- a/docs/releases/1.7.txt
+++ b/docs/releases/1.7.txt
@@ -870,6 +870,10 @@ where any unauthorized request to an admin page will be redirected (by HTTP
 status code 302) to the login page, with the ``next`` parameter set to the
 referring path. The user will be redirected there after a successful login.
 
+Note also that the admin login form has been updated to not contain the
+``this_is_the_login_form`` field (now unused) and the ``ValidationError`` code
+has been set to the more regular ``invalid_login`` key.
+
 Miscellaneous
 ~~~~~~~~~~~~~
 
diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index a84ae8c3d2..1ea9b4b657 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -17,7 +17,6 @@ from django.contrib.auth import get_permission_codename
 from django.contrib.admin import ModelAdmin
 from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME
 from django.contrib.admin.models import LogEntry, DELETION
-from django.contrib.admin.sites import LOGIN_FORM_KEY
 from django.contrib.admin.utils import quote
 from django.contrib.admin.validation import ModelAdminValidator
 from django.contrib.admin.views.main import IS_POPUP_VAR
@@ -769,7 +768,6 @@ class CustomModelAdminTest(AdminViewBasicTestCase):
         self.assertEqual(response.status_code, 200)
         login = self.client.post('/test_admin/admin2/login/', {
             REDIRECT_FIELD_NAME: '/test_admin/admin2/',
-            LOGIN_FORM_KEY: 1,
             'username': 'customform',
             'password': 'secret',
         }, follow=True)
@@ -874,49 +872,41 @@ class AdminViewPermissionsTest(TestCase):
         # login POST dicts
         self.super_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'super',
             'password': 'secret',
         }
         self.super_email_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'super@example.com',
             'password': 'secret',
         }
         self.super_email_bad_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'super@example.com',
             'password': 'notsecret',
         }
         self.adduser_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'adduser',
             'password': 'secret',
         }
         self.changeuser_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'changeuser',
             'password': 'secret',
         }
         self.deleteuser_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'deleteuser',
             'password': 'secret',
         }
         self.joepublic_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'joepublic',
             'password': 'secret',
         }
         self.no_username_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'password': 'secret',
         }
 
@@ -1391,7 +1381,6 @@ class AdminViewsNoUrlTest(TestCase):
         # login POST dict
         self.changeuser_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'changeuser',
             'password': 'secret',
         }
@@ -2600,7 +2589,6 @@ class AdminCustomQuerysetTest(TestCase):
         self.pks = [EmptyModel.objects.create().id for i in range(3)]
         self.super_login = {
             REDIRECT_FIELD_NAME: '/test_admin/admin/',
-            LOGIN_FORM_KEY: 1,
             'username': 'super',
             'password': 'secret',
         }