Gallup is out with a look today at some key indicators that look troublesome for Barack Obama's re-election prospects this fall.

There are three main indicators, which Gallup looks at from historical perspective to judge Obama's prospects this year. They are his approval rating, economic factors and Americans' view of the direction in which the country is headed.

So, first is Obama's job approval. At 47 percent in May, it compares with other presidents that have lost their bids for re-election in recent history. At this point in 2004, George W. Bush had a 49 percent approval rating. That's the lowest for a president to win re-election since 1964.

The key here is whether the number improves as we head closer to November. Bush was back up to 50 percent by October. Gerald Ford, Jimmy Carter and George H.W. Bush — three presidents that lost re-election — plummeted down to the 30s.