We should do a tiered voting system. Say there's 6 presidential candidates, Candidates A, B, C, D, E, and F, but you only support three of them. You write their names on the ballot like this:
Candidate A
Candidate B
Candidate C
The higher their ranking, the more points are tallied for them, with the max number of points available being n+1 where n represents the number of candidates.
The candidates ranking on your list determines how many points your vote for them was worth: (n+1)-(x-1) where x is their ranking on the list.
When ballots are counted, the total score for each candidate i tallied. If one candidate is unable to obtain at least 50% of the points, then lowest ranked candidate is eliminated (and their points omitted from the calculation). This will keep going on until one candidate has obtained at least 50% of the points.