Boring midwestern white dude endorses uncomfortably awkward northeastern white dude.
This endorsement changes absolutely nothing, as T-Paw adds very little value to Romney's campaign. At this stage in the campaign, it's all about the money, and T-Paw was raising an incredibly meager sum, so his value as a fundraiser for Romney is nil.
Additionally T-Paw and Romney were always competing for the same pool of marginally sane voters, although T-Paw wanted to compete for the much larger pool of crazy voters. Unfortunately T-Paw could never convincingly be crazy enough for the crazies, so he can't effectively sell the crazies on Romney, making his worth as a surrogate in the primary around zero. He's not even popular in his home state, so he doesn't even deliver Minnesota's delegates to Romney.
The only value T-Paw adds is in press attention and taking control of the news cycle, but given T-Paw's incredible inability to hold press attention for any period of time even that value is minimal. The news has largely moved past the endorsement, even though it happened today.
There are very few endorsements that matter in a Presidential race. If somebody with a specific set of dedicated voters like Mike Huckabee, or who could raise huge sums of money like Haley Barbour were to make an endorsement, then there would be some value added. But all T-Paw opening his mouth does is zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz.