You could know this before he was elected the first time, because he went out of his way to vote in favor of the program.
Actually here's some of his election promises:
"Barack Obama opposed the Bush Administration's initial policy on warrantless wiretaps because it crossed the line between protecting our national security and eroding the civil liberties of American citizens. As president, Obama would update the Foreign Intelligence Surveillance Act to provide greater oversight and accountability to the congressional intelligence committees to prevent future threats to the rule of law."
"As president, Barack Obama would revisit the PATRIOT Act to ensure that there is real and robust oversight of tools like National Security Letters, sneak-and-peek searches, and the use of the material witness provision."