This has to be one of the best slams of the Presidential election so far:

Maryland Gov. Martin O’Malley introduced a new line of attack on Gov. Mitt Romney today, saying the public should be suspicious of him because in 2008 Sen. John McCain considered the now-presumptive Republican nominee to be his running mate…but picked Sarah Palin instead.

“What about running for the office of the presidency this year makes it less important than the job that he didn’t get over Palin the last time around?” O’Malley asked BuzzFeed, referencing the 23 years of returns Romney allowed McCain to examine while he was being vetted but hasn’t released to the public.

Pressed in an interview at the National Governors Association meeting here whether there would be anything in those returns that would disqualify Romney from the presidency, O’Malley said he doesn’t know — and that’s why Democrats want to see them.

“But why would you pick somebody — why would you pick Palin over Romney?” he asked.

(emphasis mine)

Sweet!