ssl_requirement ajax call from non https to https

I have a page that has nothing on it that needs to be secured by SSL,
except when someone wants to hit an ajax request to login.

I don't want to secure every page, just so that when I render a
partial that needs to be https, it'll be protected.

I'm using the ssl_requirement plugin.

Any ideas on what to do? Is this even possible? Or will I have to
encrypt every single page? I'd rather not do popup windows,
everything's nice and slickly inserted with cool DOM manipulation.

Thanks!