"Not voting" is not interpreted by the media (and thus the public consciousness) as dissatisfaction with the given options. It is interpreted as anti-patriotism, carelessness, or ignorance.
A 3rd party vote despite the prevailing wisdom of them being wasted is slightly more resistant to these types of reductionist criticism, but still not as powerful as a "no confidence" vote would be.
A 3rd party vote despite the prevailing wisdom of them being wasted is slightly more resistant to these types of reductionist criticism, but still not as powerful as a "no confidence" vote would be.