In the Merovingian and Franconian Empire, a Graf ("Count") was an official who exercised the royal prerogatives in an administrative district (Gau or "county").
The most powerful nobles and bishops (Electors) secured the exclusive privilege of voting to choose a Holy Roman Emperor, from among their own number or other rulers, whenever a vacancy occurred.
[1] As the Empire emerged from the medieval era, immediate counts were definitively excluded from possessing the individual seat and vote (Virilstimme) in the Diet that belonged to electors and princes.
They participated with the emperor, electors and princes in ruling the Empire by virtue of being entitled to a seat on one of the Counts' benches (Grafenbank) in the Diet.
The decrease reflected elevations to higher title, extinction of the male line, and purchase or annexation (outright or by the subordination known as mediatisation) by more powerful imperial princes.
In 1792 there were four associations (benches) of counties contributing the votes of 99 families to the Diet's Reichsfürstenrat: By the Treaty of Lunéville of 1800, princely domains west of the Rhine River were annexed to France, including imperial counts.
By 1806, Napoleon's re-organisation of the continental map squeezed not only all imperial counts but most princes out of existence as quasi-independent entities by the time of the Holy Roman Empire.
In 1815 the Congress of Vienna sought to turn back the clock on the French Revolution's politics, but not on the winnowing of Germany's ruling dynasties and myriad maps.
Titles granted by Habsburg rulers in their capacity as Kings of Hungary, Archdukes or Emperors of Austria were not thereby Reichsgrafen, nor ranked with comparable precedence even post-1806.