It has been a long time since a prince toppled a prime minister.

But this is what could happen in Australia. When the adamantly monarchist prime minister, Tony Abbott, announced that he was going to make the heavily titled, gaffe-prone Prince Philip a knight, the nation laughed — then groaned. And now, as a direct result of his action, his party will be voting this Monday to decide whether it should be allowed to vote for another leader.

It was not that Mr. Abbott’s ardent affection for the royals was a surprise. He previously served as executive director of Australians for Constitutional Monarchy and at his signing in, he swore allegiance to the queen, unlike his two predecessors, Julia Gillard and Kevin Rudd.

One of the first things he did after becoming prime minister was to try to find a copy of a portrait of a sensuous, curvy Queen Elizabeth II in a yellow evening dress, from 1954. Prints of this portrait, painted to mark a wildly successful royal tour the year after her coronation, hung in thousands of schools, scout halls and churches for decades; she was adored and held in awe. But in the 1970s these images began slowly vanishing, seen as relics of a dated, less proud Australia. After the British-born Mr. Abbott hung the portrait with pride in his office in Parliament House, one staffer grumbled to a reporter: “Next they’ll be making us curtsy when he comes into the building.”

It was not long before Mr. Abbott — astonishingly — decided to reinstate the British honors system of knights and dames. In an attempt to diminish criticism that might ensue, the first dame he appointed was the then-governor general, Quentin Bryce, who was in favor of moving from the country’s current constitutional monarchy to a republican form of government.