Donnie Nelson has a saying: You can never have enough shooters.
That pretty much sums up why the Mavs are interested in Al Harrington, whom they have offered the full midlevel exception.
Harrington is an outstanding shooter for a power forward. The problem with the Mavs' pitch: They have an even better shooter at power forward who is guaranteed to get the bulk of the minutes.
It'd be a luxury to have Harrington back up Dirk Nowitzki. However, Harrington could probably find more minutes elsewhere.
The Nuggets are also trying to sign Harrington. Denver has a significant need for a power forward due to Kenyon Martin's injury issues.
It's a long shot that Harrington would opt for the Mavs over the Nuggets.