Ambition is the last refuge of failure by Oscar Wilde

I heard this quote watching one of the episodes of the CSI TV series. At the end of the episode, the lead scientist of the crime lab was asked if he has ambition to take on more responsibilities in the same sense of a promotion. The lead scientist replied, “Ambition is the last refuge of failures”.

Being as curious as I am, I started looking into this quote from the internet and try to find out its exact meaning. It returns different meanings.

Some said, it means that ambition breeds failure because through ambition that one is more finely tuned to failure.

Some said it’s through failure one becomes more ambitious.

Some also said, it means exactly what it’s read. Ambition is the last protection or shelter of failure. So, failures are OK when there are still ambitions.

I thought ambition is what gives the person the will to success. But this quote almost implies the exact opposite of that point. It’s almost saying that one will eventually fail if he has ambitions. It's really contradictory.