People have been both skeptical and cynical on both sides of the Bush tax cuts for the wealthy in 2010. On one side, many think that it will harm the economy and not help, but on the other side they do not know how much it will help out the economy.
I don't see there being "cynical motivations" in expiring the tax cuts, nor in extending them. I merely believe that extending them is an unwise or strategically bankrupt stance. Basic economics shows that allowing people at the bottom to flourish more means they purchase more goods and services, which floats to the top naturally anyways.