Politico reported the news yesterday, and here is the official Obama camp release from today:

Chicago, IL--The Obama campaign today announced that Senator Hillary Clinton will campaign for Senator Obama in Nevada and Florida later this month. Senator Clinton will host Campaign for Change rallies and voter registration events in Las Vegas, Nevada on Friday, August 8th and in South Florida on Thursday, August 21st.

Here are some possible explanations for the strategic decision to have Clinton campaign in these two states:

Nevada has voted Republican in eight of the last 10 presidential elections, with the only two exceptions coming in 1992 and 1996, when it supported Bill Clinton. In 2004, Pres. Bush carried the state by only 2 points.

In Florida, Hillary Clinton defeated Obama by close to 17 points in the January primary. The only Democrat to win the state in the last seven presidential elections was Pres. Clinton in 1996. Although Bush extended his winning margin to 5 points in 2004, the race is currently tight in Florida, with McCain leading by just 1.6 points in the RCP Average.