Best way to publish to Drupal using WordPress?

I’m working with a client to develop a site with the goal of producing content once while publishing twice.

She would like to interface with WordPress, but the CMS for her larger organization is Drupal.

I haven’t yet reached out to the admin of the larger org but I expect a directory could be set up to mirror the content for the WordPress site I will set up and potentially host elsewhere.

That is unless there is an easy way to use the WordPress interface to manage content through Drupal.

I’m sure I’m not the first to experience this issue, and I can imagine some cumbersome solutions, but I’m interested in the one which is least painful ongoing. Lots of work up front is acceptable. Manually exporting and importing posts is not.