Strengths and weaknesses are relative. That is, whether some trait is a strength or a weakness seems to depend on the circumstances. I reckon that’s as true of President Obama as it is of anyone else.
President Obama apparently likes to find the shared values and interests between himself and others and build alliances based on that common ground. One can easily see how that would be a strength in some circumstances.
Unfortunately, it doesn’t appear to be much of a strength when your enemies are adamantly opposed to you, won’t give an inch, and desire nothing more than you fail. President Obama seems to be facing that sort of opposition from Congressional and Senate Republicans. So far as I can see, the Republicans have not been working with President Obama even when it would be in their interests to do so. Instead, they have simply opposed anything he’s for.
I suspect President Obama’s instinct to find common ground with the Republicans contributed to the Stimulus Package being too small and somewhat misdirected. If so, then that would be an example of where one of his traits became a weakness.