What political causes has Buchanan focused on? How might that influence his evaluation of a free trade agreement like NAFTA?

James M. Buchanan, an American Economist of libertarian thinking, has focused on the theory of Public Choice.

Explanation:

In this theory, Buchanan argues that policy making is affected by the self-interest, amd desire for utiliy maximization, of the bureaucrats.

Like this, he argues, bureaucrats are not government officials who are only interested in the well-being of society as a whole, but on the contrary, people who have vested interests like anyone else, and who modify the public policies according to those vested interests.

Buchanan would evaluate the NAFTA in negative terms because he would argue, like most libertarians, that while such agreement is an advancement towards free trade among nations, it is still full of flaws that come from the fact that it was drafted by bureaucrats that had vested interests during the drafting process.