• We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
I think it's only possible via revolution to something, then to democracy. I don't think you'd get democracy even if you take away all voting rights (can you return to absolute monarchy, in other words), then grant universal suffrage.

So either calm them down, or let the rioters take over, suffer the prestige hit, and then establish democracy.
 
Get a radical party in power. Somehow. It will become a Presidential Dictatorship.

Revoke voting rights and make it a single-party system if the event doesn't.

Next month, enable free parties.

After the event fires telling you you changed the constitution, switch to a moderate party, and allow universal suffrage.

An event will fire turning you into a democracy.