I think you need to prevent a Tory split for that to work. And more importantly, prevent the Whigs pivot to being pro-free trade and instead maintaining their old mercantilist policy.
OOOOOOO
How about, a world where the American Revolution never happens and the French Revolution remains pretty quiet, mostly just reforming into a Constitutional Monarchy. The Whigs remain the dominant party but their factionalism slowly turns into new formal parties, with the Radicals becoming this world's Liberals, upholding the principal of free trade, calling for the widening of the franchise and other constitutional reform, while the rest of Whigs remain committed to protectionism and the power of the 'country interest'.
