The argument tells us that the road is needed for the complex, and that the complex will guarantee development. So, everyone should vote for the road tax.
We do not actually know that the project is necessary to strengthen the economy. We know it is sufficient, but not that it is necessary. Maybe they could improve the economy by opening a school, or changing their tax policy?
However, we know that the road will benefit everyone, and if everyone should vote for something that benefits them, then the argument is valid.
