For all its stupidity, Cory Bernardi's defection has already shifted the needle in Canberra, strengthening the right's grip, and ensuring that 'moderate Malcolm' is consigned to history.

Superficially, Bernardi's crazy-brave gesture had two relatively benign implications for Turnbull beyond its initially poor optics: the removal of a pesky internal critic (good); and, the prospect of an even less compliant Senate (business as usual).

What is more important however, is that the defection has given material form to what, until now, was just a theory.

Rendered in flesh and blood, the risk to Turnbull is now very real and crucially, is more likely come in the House of Representatives where the Coalition's majority hangs on a single seat.