I think the straw that broke the camel’s back was Al Gore’s reaction to losing the presidential election in 2000. he paved the way for the “Never [fill-in-the-blank]ers” to ply their trade.
They've been off the rails ever since.
That may have been the straw that broke the camel’s back, but the camel’s back was bent to near-breaking by the ginned-up phony Watergate “scandal” and then by inability of anybody to bring the Clinton’s to justice for all their crimes going back to Whitewater / Arkansas Land Development Corp, cattle futures graft, etc. An honest Republican was hounded out of office by the rabid democrats, then the same democrats skated free as birds a few years later.
The camel has been groaning for a long time.