Multiple PasswordProtectedTransport login handlers

[Brian Reindel]

I have two login handlers. One handler is of type ph:UsernamePassword,
and the other is of type ph:ExternalAuth, but both of the
authentication methods for those handlers are set to
urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport. If
I specify that as the defaultAuthenticationMethod in the IdP relying
party configuration for multiple service providers then how does it
know whether or not to use the ph:UsernamePassword or the
ph:ExternalAuth?