I wrote this procedure for a session of my Great and Terrible duet campaign.
This is the procedure that involves an improbably melange of D&Disms and industrial American political process, but it can make for a fun session. Assume I'm familiar with all the potential historical exceptions and simplifications this procedure needs to work.
First you have to define the position that candidates are running for, who is eligible to run and what the domain of eligible voters is. Presumably if you're using this procedure you've already got that selected.
Next, you make an election map. This divides the constituency into a discrete number of localities whose votes can be won individually. There will be "regions" which contain multiple "districts." Divide the constituency into two or more regions which contain three or more districts each. For my playtest I divided Fantasy Wild West California into four regions with a total of fourteen districts.
For each region, the DM should note down a secret "lead," a hook that may lead to an advantage in the election if discovered.
If a region doesn't have much voting power, it will have fewer districts than other regions. Often you will want to represent a place with a lot of voting power, like a city, with multiple districts, though some electoral systems will emphasize or deemphasize the power of population.
Next, you will want to briefly list a few preferences for each district. They may favor certain policies or interest groups, or candidates who are like them in some way. Keep it short, and if you are one area with multiple districts, try to change up each district in that place. Take a very light touch on giving districts hard party preferences, since it's more fun if a district is at least theoretically in play for multiple candidates.
Before the procedure gets into Campaign Turns, the DM should make sure there are two or more candidates, including any PCs. They should assign positions and characteristics that are relevant to the preferences of the various districts. When there are multiple NPC candidates, a DM can choose their actions on the trail mostly at random. When there is only one, they may want to be choose more carefully.
The DM should also construct an Event Roll table. They may also assign a bonus point of Momentum of a particular kind to each candidate. Both are described below.
Winning the Game
On election night, the DM will run through all the districts and decide up to two candidates who are most likely to win that district based on its preferences and their actions during the campaign. If only one candidate has a chance, they get 1 Vote Point. If there are two, both roll a d6 and the higher roller wins the Vote Point . On a tie, candidates may opt to spend $100 times the amount just rolled on their die to double down. In that case, if only one continues they get the point. If both spend the money, they roll again. If a candidate loses a die roll, they may choose to spend 1 Momentum (described below) to reroll and force their opponent to reroll.
Before the election night, there will be six Campaign Turns roughly representing roughly a month (the first turn being longer and the last turn squeezed into the last few days of the election).
At the start of each Turn, the DM rolls on a d6 Event Roll table, which should be populated with major issues relevant to the voters, such as relations with a nearby nation or culture group, or some economic problem. They should let the issue rolled inspire them to come up with a more specific event. For instance, an entry on the table might be the competition Rural vs Urban interests and the specific event a DM comes up with might be the uncovering of a previously-beloved weather wizard embezzling from farming interests, which may make a candidates appeals to farmers seem less-well considered than otherwise.
Also at the start of the Turn, each candidate must spend 1d4+5 x $100 just to stay in the race. Those who can't or won't are considered to have dropped out.
During the Turn, a candidate can lead their campaign in a variety of ways. They generally fall under the following categories:
Grand Tour: Visit every region in the constituency. The DM should give them hints for anything notable happening, and reveal two or three of those leads they prepared earlier.
Visit: go to a specific region or district to campaign. If their approach is apt and appeals to the area in question, they get 1 point of Momentum which they can spend to force a reroll in that area on election night. DMs should be more stingy giving Momentum for regions than for districts. If the approach is marginal, ask for a reaction roll or something to see if they pull it off. While conducting a visit, the candidate and their campaign staff should be allowed to follow up on a lead in the same region as the area they are visiting.
Fundraise: Ask donors to contribute to the war chest. If they can appeal to the wealthy or make themselves popular, a good amount to give would be 2d4+10 x $100. If they make major concessions to the wealthy, maybe go with 1d4+15 x $100.
Counter: Learn what another candidate is doing as they do it and attempt to interfere. If done with the right approach, you can prevent them from getting Momentum.
Debate: go head-to-head in a formal display of argument with another candidate. The victor as determined by a reaction roll, modified by approach and the crowd of the district in question, steals 1 relevant Momentum from their opponent.
Stunt: anything else. This may be a political risk and should have the potential for commensurate reward.
It's not the most in-depth election simulation, but it has enough structure to come alive when you characterize the events and actions of the NPC candidates with zeal and creativity. I prerolled the Events for each Turn as well as the intended actions of the candidates in the election I ran, and it kept things moving at a brisk pace. Would love to try this with multiple PC candidates.
In the playtest, there wasn't a cadre of secondary PCs who wanted to further influence the election. If a PC's staff includes other active player characters, a DM may want to furnish the other candidates with a few capable henchmen or award them some bonus Momentum.