Minimum Wage Realities.

A Quick Look at the Federal Poverty Level Guidelines Used for 2013, 2014, 2015, 2016, and Beyond Persons in Household  2013 Federal Poverty Level threshold 100% FPL  (first pair of columns)
1    $11,490    $5.52
2    $15,510    $7.46
3    $19,530    $9.39
4    $23,550    $11.32
The current federal minimum wage is $7.25 per hour. A full-time minimum wage employee earns $15,080 annually.  In 2012, the poverty threshold for a single person was $11,945. For a family of four with two children it was $22,283.
To qualify for public assistance a household needs to have a per-person gross income less than less than the second pair of columns.
1    $16,086    $7.73
2    $21,714    $10.44
3    $27,342    $13.15
4    $32,970    $15.85
Working 40 hours/week 52 paid weeks/year means 2080 hours requires column 2 free of taxes and transportation to and

from work, or net of work related costs and taxes, roughly the amount in the third pair of columns.
1    $20,108    $9.67
2    $27,143    $13.05
3    $34,178    $16.43
4    $41,213    $19.81
Raising the minimum to $15 places single individuals well above poverty and provides them with enough disposable

income to boost their local economy significantly. 
That means more demand for goods and services and more job opportunities. 
PLUS they are off welfare and paying taxes, thus reducing government costs and increasing government revenues. 
Their money will also lift revenues for Social Security and place it on a firmer footing.
Since the benefits achieve everything Republicans allege they want to achieve, the reason for their opposition is clear -- as with everything else REPUBLICANS ARE LIARS who want to hurt the economy by undermining it at the grassroots level ... basically poisoning the roots so the National tree will die.