gistfile1.js

jQuery(function($) {
  // create a modal view class
  var Modal = Backbone.Modal.extend({
    template: _.template($('#modal-template').html()),

    viewContainer: '.modal-view',

    views: {
      'click #first': {
        view: _.template($('#modal-view1-template').html())
      },
      'click #second': {
        view: _.template($('#modal-view2-template').html())
      }
    }
  });

  // render an instance of your modal
  var modalView = new Modal;
  $('body').append(modalView.render().el);
});