Liberals, of course, don't want anybody focusing on Obamacare,because even they know, but will never admit, that it's an unmitigated disaster. Essentially, Milbank is suggesting that Obamacare isn't what Americans are concerned with and the economy is. Two problems with that train of thought.
First, Obamacare and the economy are hardly mutually conclusive. Businesses are terrified of what it'll do to their bottom line and individuals are in a spending crouch because they're not sure how much more their insurance will cost. To say Republicans are obsessed with Obamacare is like saying Democrats in 1973-74 were obsessed with Watergate.
The difference is Obamacare direclty, and adversely, impacts the lives of individual Americans.