The article itself is about four ways Republican and Democratic health care reform plans are similar, including agreement that competition is good, an insurance mandate (Democrats penalize those who don't buy insurance while Republican plans reward those who do), taxing the rich (means testing is taxing the rich as well), and blinkered optimism - the staunch determination to not consider what will happen if their plans fail. (You'll have to read the article if you want to know why Mankiw makes these arguments.)
Then, at the bottom of all this there is Mankiw's bio line:
N. Gregory Mankiw is a professor of economics at Harvard. He is advising Mitt Romney, the former governor of Massachusetts, in the campaign for the Republican presidential nomination.So that's why he's writing about health care reform!