The Left never relents. It never relaxes its pressure against the vessel, particularly where there is the slightest sign of a leak. Their hope is always a rupture to take advantage of, a flood. The Right can scurry to repair the spill but they never are able to put the spill back into the vessel. Meanwhile, the pressure of the Left remains inside the vessel.
That is how the Left gains ground; first a leak, then a flood, always pressure.
I need coffee.