How to use jQuery Validation plugin with form-level server-side validation?

What's the best way to trigger errors on elements for server-side validation errors that come back after the form passes the initial client-side validation?

$("#contact_form").validate({
  submitHandler: function(form) {
    $.ajax({
      type: 'POST',
      dataType: 'json',
      url: '/contact/send',
      data: $(form).serialize(),
      success: function(response) {
        if(response.error) { //server came back with validation issues
          var fields = response.fields;
          for(var i=0, var len = fields.length; i < len; i++) {
            var field_name = fields[i].name;
            var field_error = fields[i].error;

            // TRIGGER ERROR ON AFFECTED ELEMENT

          }
          return false;
        }
        //everything went ok, so let's show a thanks message
        showThanks();
      }
    }
});

I'm thinking something like:

$(form).find("[name='" + field_name + "']").triggerError(field_error);

But I didn't see any api methods for manually triggering errors in that manner.