Short answer: In the short to mid term, poor and middle class in the outsourcing country do poorly. Ultimately, there may be a sufficient gain for the overall economy that everybody wins, but if demand for low-skilled labor is limited, it may take a long time till "ultimately".
On an individual level, the question is, unfortunately, very difficult to answer. You would need to have access to the employment history of a large number of people in order to make any significant statement. Such data simply do not exist.
One recent study (Autor, Dorn, Hanson: "The China Syndrome: Local Labor Market Effects of Import Competition in the United States" (pdf); see also the article about it in WSJ) has looked at the effect of imports from China on local US labor markets: What happens to a local labor market when the country is importing lots of products that were traditionally produced by the local labor market (commuting zone, CZ)?
Our results suggest that the predominant focus of the previous
literature on wages misses important aspects of labor market
adjustments to trade. We find that increased exposure to
low-incomecountry imports is associated with rising unemployment,
decreased labor-force participation, and increased use of disability
and other transfer benefits, as well as with lower wages, in affected
local labor markets. Comparing two CZs over the period of 2000 through
2007, one at the 25th percentile and the other at the 75th percentile
of exposure to Chinese import growth, the CZ at the 75th percentile
would be expected to experience a differential 4.5 percent fall in the
number of manufacturing employees, a 0.8 percentage point fall in the
employment to population rate, a 0.8 percent fall in mean log weekly
earnings, and increases in per capita unemployment, disability, and
income assistance transfer benefits on the order of 2 to 3.5 percent.
Interestingly enough, they find that while wages in the directly affected industries are stable, wages of other low-income jobs decrease, because companies lay off the less critical workers first, who then have to find something else in a different sector. Thus, at least in the short to medium term, life gets worse for the majority of low-income workers when people are laid off, even those who weren't working in the affected industries.
The study cannot differentiate whether the job losses are due to companies shifting manufacturing overseas, or whether they are due to Chinese companies simply outcompeting US companies, but for the purpose of the article in the OP, the US should be benefitting in both cases.
Along with the increase in unemployment, there is a rise in disability benefits, since people who may otherwise prefer to hold a job fall back onto whatever is available to keep them afloat. Since these benefits ultimately have to be paid via taxes, the authors of the study can estimate roughly how much the US is spending vs gaining from imports from China, and they come to the surprising conclusion that
The deadweight loss of financing these transfers is one to
two-thirds as large as U.S. gains from trade with China.
In the long run, the US either finds a way to generate jobs for these people, or it will lose importance as an economic superpower. However, in the short run, the effect on low-income workers are not that great, and the gains for the overall economy, which may or may not trickle down to the low-income workers, aren't quite as amazing, either.