Attorneys for the ex-governor say the president's testimony could clear up issues about Obama's old Senate seat, which Blagojevich is accused of trying to sell.
Chapman University law professor Ronald Rotunda says a some sitting presidents have been subpoenaed in criminal cases. Take James Monroe, who testified on behalf of a colleague.
ROTUNDA: The charges were "intrigue and misconduct." That is, "you got your offices in a bad way," is what we would say now.
Presidential testimony most recently came from Bill Clinton, who was sued for sexual harassment. Clinton argued he was too busy to testify.
Rotunda says that argument didn't work for Clinton, and it wouldn't work for President Obama.
ROTUNDA: He's a normal human being. He goes to parties, plays golf, he takes his wife on a date to New York City. The Supreme Court said unanimously the President is subject to the processes of the court.
The White House is not commenting on Blagojevich's request. Blagojevich has pleaded not guilty.