The most credible and reliable support for the argument in favor of lowering the age to get a driver's license to 14 years of age would be:
a national news broadcast reports that in South Dakota, teenagers as young as 14 years old can receive their restricted drivers permits.
This choice provides factual evidence of an existing policy that allows 14-year-olds to drive in a specific context, which lends legitimacy and demonstrable precedent to the argument for similar changes in the writer's state.