Amsterdam burgemeester in 1781. Like many other regents of the States Party, he opposed the stadtholder's tutor, Duke Louis Ernest of Brunswick-Lüneburg, who held a sinister hold over the stadtholder according to the Acte van Consulentschap. Rendorp petitioned the stadtholder in April 1781 on behalf of the Amsterdam city administration, requesting the Duke's removal from the Dutch government. The stadtholder became enraged as a result, and Rendorp lost a lot of support from the public because of his lack of moral bravery in the face of this confrontation.
Rendorp welcomed Joseph II, the newly appointed Austrian emperor and sovereign of the Austrian Netherlands, when he paid an undetected visit to Amsterdam that same year. wherein he talked on a variety of contemporary political topics, including as the Scheldt's closure to shipping, which was a major concern for Amsterdam at the time, and the Barrier Treaty, which would soon put the emperor and the Republic at odds. Joseph stressed the importance of achieving peace with Great Britain as soon as possible and suggested using the Sardinian consul Triquetti as a go-between. This attempt at private diplomacy was fruitless as the emperor made the identical proposition to the French envoy, de la Vauguyon, who promptly put an end to the peace feelers. Later, Rendorp attempted unofficial peace talks with former envoy Yorke and England secret agent Paul Wentworth, but these attempts also ended in failure.
Rendorp did not clearly identify as a Patriottentijd partisan. In addition to the "democratic" faction of the Patriots, he opposed the stadtholder. With his reelection as burgemeester in 1786, he made an effort to suppress that faction, believing that the Patriot Revolt had already progressed sufficiently and that the States Party's objectives had already been fulfilled by the stadtholder's diminishing authority. He was frequently the target of criticism
in the Patriot press, including the Post van den Neder-Rhijn, due to his "moderate" posture. As an Amsterdam magistrate, he had the authority to respond immediately. In 1785, he personally fined and even imprisoned a number of journalists and publishers for publishing defamatory articles about him.
In the 1787 Burgemeester election, Hendrik Daniëlsz Hooft, a Patriot, defeated Rendorp. As a result, he was forced to watch from the sidelines while Colonel Isaac van Goudoever led the uprisings that resulted in the fall of the Amsterdam city government in April 1787. His house was among the Orangists' that the Patriots plundered when the Bijltjesoproer broke out at the end of May 1787.
With the Prussian incursion into Holland and the collapse of Amsterdam on October 10, 1787, Rendorp was re-admitted into the "rehabilitated" municipal administration. In 1789, 1790, and 1792—the year of his passing—he was once more elected.
== Activities ==
Dealing with the Regt of the Jagt (1771), Dedicated to the Prince of Orange
Over de Militaire Jurisdictie (1775)
Memoriën, dienende tot opheldering van het Gebeurde, geduurende den laatsten Engelschen oorlog (1792)
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