In line with other things Tim Keller has written, I think he has articulated the Christian’s position within politics well. The only thing I disagree with is claiming that helping the poor and fighting racism “seems liberal” when the distinction between left and right is how to address these, not whether to address these. While some on the right do at times use rhetoric which may suggest otherwise, it is currently the left advocating for racially segregating dorm buildings on campuses and other such policies. The problems of not caring for the poor and racism know no party affiliation. (While there are also those who are left-leaning who do want there to be a biblical sexual ethic, and while clearly politicians on the right have not proved to be bastions of sexual ethic, I think the other issues illustrate the point better.)
In this way the article could seem to advocate a sort of “middle party” that is an amalgamation of our two parties, taking the best and leaving the rest, or even advocating for a third centrist party. I don’t believe that’s what he is doing, but if that’s what some take away from this I believe they’ve missed the point. While we have to operate within the limits of our government, and as Keller argues that we cannot be apolitical, I don’t think Christians are to be centrists, who are as much a political party as the other two.
See some of his other posts here.