[Romney] only plans to release his return for 2010 and an estimate of his returns for 2011. That might have been enough prior to the controversy. George W. Bush only released one year of his tax returns. But it won’t work now. As Buzzfeed’s Ben Smith tweeted, “Releasing the 2010 returns is just blood in the water. What about the previous 20 years?”
That's especially true given his father's example.