Turns out, it was the real Obama:

According to a statement released by her office, the Republican congresswoman cut off the caller, telling him she thought “this is a joke from one of the South Florida radio stations known for these pranks.” She then hung up.

Finally, an aide told Ros-Lehtinen she had an urgent call from Chairman Howard Berman, chairman of the Foreign Affairs Committee. Still suspicious, Ros-Lehtinen urged the California Democrat to recount a story only both of them would know.

Berman passed the test — and told her she had, in fact, hung up on President-elect Obama.

Oops! CNN’s Political Ticker has the story: Link