sorry ... wicki
A rump legislature is a legislature formed of part, usually a minority, of the legislators originally elected or appointed to office.
The word "rump" normally refers to the back end of an animal; its use meaning "remnant" was first recorded in the context of the 17th century Rump Parliament in England. Since 1649, the term "rump parliament" has been used to refer to any parliament left over after the true parliament has formally dissolved.
In the United States in the 19th century, upon the secession of Virginia from the union on April, 27 1861, anti-secessionist legislators convened a rump legislature and formed a pro-Union reformed government which claimed to represent all of Virginia. This reformed government authorized the creation of the state of Kanawha, later renamed West Virginia. By contrast, the Legislative Yuan of the Republic of China between 1951 and 1991, having been relocated from Nanking to Taipei when the country lost its mainland in late 1949, contained members originally elected from mainland constituencies who could not be replaced. The pre-reform Legislative Yuan was nevertheless widely regarded as a rump legislature, controlling only a fraction of the territory it claimed to represent.
Rump is used correctly, but why not “faction?”
Rump also means “backside” or “ass.” I believe that that is why the author was trying to imply... “A group of Republican a-holes...”
And don’t forget Heinlein using the phrase in “Starship Troopers” - the army had to form a “rump battalion” out of shattered remnants of other units.
This was a deliberate choice of words, as they knew that people would associate “rump” with “ass”.