In the 1969-1972 tax years, Nixon paid only 7% of his average income in taxes. Nixon went on national TV and famously said "I am not a crook" when in reality he was the worst kind of crook. He was ripping off the entire nation. Fortunately Nixon was caught and was forced to pay hundreds of thousands of dollars in back taxes.
Romney doesn't appear to be a crook in the literal sense. He steals from the nation legally. Instead of going on national TV and declaring he isn't a crook, he goes on national TV and declares he shouldn't be taxed at the same rate as working Americans because he's a "job creator". Study after study has shown that taxing capital gains at lower rates yields no significant economic benefits.
The reality is that Romney and Nixon are cut from the same cloth. They both had no remorse in going on national TV and lying to the public. They both appear to share the belief as Leona Helmsley in that only the "little people" pay taxes.