Directly and democratically elected legislature with an elected supreme court. Semi-elected monarch as executive; however, the monarch holds no power unless there is an unresolved gridlock in the legislature, at which point the monarch can break the tie. Instead of a president you have consuls, who are elected directly from a pool of existing senators/representatives. When voting for a consul, you may choose a primary (counts as 1 vote) and a secondary (counts as 0.5 votes). This encourages moderate candidates, as while different people might have vastly different primary picks, they are likely to agree with a moderate as a secondary pick, discouraging divisive elections. Non-citizen permanent residents (such as immigrants with green cards) may only choose a secondary pick, giving them some voice in the government while still enabling citizens to have a majority voice.
Unlike consuls in Rome, however, there would be a primary consul and two secondary consuls elected. Consuls would function more as super-senators than executives, having the ability to propose a public assembly (which would allow a proposed bill to be directly voted on by the citizen body) and their votes count as three or five times as much as that of a regular congressman (3 for secondary, 5 for primary consul).