1. Check the source code.How do you do that?
2. Lines 200 and 201 define which candidates go in which election. Copy these, and use inspect element.
3. Paste the lines into the console and move around the candidates. They appear as numbers so you have to figure out which number corresponds to which candidate, and which number corresponds to which election. (Line 205 defines the election years.)
4. This only seems to work for playable candidates. Modifying the minor candidates breaks the game. The candidate you play as cannot be deleted from the election either.