The new criticism centers on adviser Eric Holder Jr., who is vetting candidates to be the presumptive Democratic presidential nominee's running mate, the Washington Times said. As deputy attorney general under President Bill Clinton, Holder reviewed the controversial, last-minute pardon of fugitive financier Marc Rich.

Charged with 51 counts of fraud, tax evasion and illegally trading with Iran, Rich fled to Switzerland in 1983 but won a pardon from Clinton in 2001, prompting a congressional investigation because Rich's wife was a major Democratic donor.

"I think it is a matter of record that Mr. Holder recommended the pardoning of Mr. Rich," Sen. John McCain, R-Ariz.,the presumptive Republican presidential nominee, told reporters.

The Republican outcry over Holder came a day after Obama adviser Jim Johnson, who was leading the vice presidential search team, resigned amid questions about his Wall Street dealings.