Some context: This was built for a hackathon + I'm currently using the test API keys for Phaxio intended for testing, so the congressperson currently doesn't actually get the fax unless I swap the keys out for the live ones. It does, however, give feedback as though the fact has been sent, so feel free to try it out.
To me the ideal use case of this would be the pressure tactics employed by orgs like the EFF or ACLU during times of protest. For example, when Net Neutrality was a significant mainstream issue, orgs had tools to reach out to your specific Congressperson to persuade them to vote in favor of Net Neutrality; those tools involved several steps, and from a UX perspective condensing it into one step would create more participation. Plus, physical faxes are pretty hard to ignore.
To me the ideal use case of this would be the pressure tactics employed by orgs like the EFF or ACLU during times of protest. For example, when Net Neutrality was a significant mainstream issue, orgs had tools to reach out to your specific Congressperson to persuade them to vote in favor of Net Neutrality; those tools involved several steps, and from a UX perspective condensing it into one step would create more participation. Plus, physical faxes are pretty hard to ignore.