Manchin's not a "problem." He is just one of the people who are stating that they disagree with the idea floated by some that $15/hr should be the very minimum wage for the very poorest part of the country.
First, I'm not here suggesting that people should just be able to live on $7/hr. Heck, I couldn't live on $15/hr.
I think there are two problems with the floated federal $15 minimum wage. First, as I posted earlier, I think trying to decide a basic minimum wage on a country wide basis encompasses too broad a group. I think doing it on a city wide basis approaches a too narrow a group problem, but barely. I think a statewide minimum wage, while not perfect, is a decent compromise. If we're going to have a federal minimum wage, I think it should err on the low side so as to not impede too much on the state determinations.
Second, moving the federal minimum wage from $7 or $7.25/ hr or whatever it is now to $15/hr is simply too big a boost for some areas of the country. Minnesota has been raising their minimum wage every year now for a number of years. States like California or NY have maybe already approached $15/hr, or exceeded it. Thus, this move would have a minimal effect on Minnesota, NY and CA. But for states still dictating a $7 or $7.25/hr minimum wage, making them double it is simply too much too soon.