This is a reboot of my previous thread on this POD:
There can be little doubt that when it comes to influential Supreme Court Chief Justices, John Marshall sits at the top. The rulings of his court were crucial to the expansion of the Supreme Court's power, and the supremacy of federal law.
Having said that, what if Marshall was never appointed Chief Justice? His predecessor, Oliver Ellsworth, resigned due to illness he had contracted after returning from France as Envoy Extraordinary. The POD is pretty simple - Ellsworth avoids his illness, and stays on CJ until his OTL death in 1807. Ellsworth was a Federalist, and it seems likely he wouldn't rule any differently than Marshall on the cases he heard (crucially Marbury v. Madison). But after his death, this changes, as Jefferson will certainly appoint someone from his own faction.