(Expanding my previous thoughts)
Sen. Blanche Lincoln favors serious financial reform, including forcing financial institutions to spin off their highly profitable derivatives operations. The banksters really don’t want this to happen.
So, did Wall Street use organized labor as proxy or an ally to try to defeat her? Both factions wanted her gone and it seems impossible that financial interests would not actively work to see her go down.
While labor can certainly be a progressive force, it rarely has been that for quite some time in the US, and is too often part of the problem and not part of the solution. So, I see no need to blindly support labor, it depends on the circumstances.
Maybe her views on financial reform was a major factor in her victory.