This week's featured article at the Sobel Wiki is on Thomas Kronmiller, leader of the radical wing of the People's Coalition from 1893 to 1908.
The use of "radical" rather than "leftist" is deliberate, because in the Sobel Timeline, the lack of a successful French Revolution means that the left-right metaphor for political alignment is never established. Kronmiller is a radical because he wants the government to be more egalitarian than does Ezra Gallivan, the leader of the Coalition, as well as the head of the party's moderate wing. When he becomes chief executive of the Confederation of North America in 1888, Gallivan does not try to redistribute the country's wealth (or at least, Sobel doesn't mention him doing so). Instead, he repurposes the National Financial Administration into a sort of quasi-governmental venture capital firm, issuing business loans to start-up companies in return for equity stakes, and funding the loans by issuing bonds rather than using tax revenues.
Gallivan himself was more radical than his predecessor, John McDowell, but Gallivan emphasized spending cuts and tax cuts. Gallivan was also, unlike McDowell, a fervent isolationist, reducing military spending and ending McDowell's efforts to forge closer ties with the rest of the British Empire. Kronmiller, even more radical than Gallivan, was also less isolationist, being an adherent of the Moral Imperative, a social movement that sought to expand North American influence in the rest of the world (which Kronmiller called "the North American mission.") Unlike McDowell's Liberals, Kronmiller's radical wing of the P.C. wanted the C.N.A. to act on its own behalf, rather than in concert with the British Empire, which the radicals regarded as hopelessly reactionary. Thus, during the wave of hysteria that followed the Mexican invasion of Russian Alaska in 1898, Gallivan had to fend off both the radical interventionists led by Kronmiller, and the reactionary interventionists led by McDowell's protégé Douglas Sizer. It may have been their diametrically opposed ideologies that kept Gallivan's numerically superior enemies from combining to oust him from power at the height of the Starkist Terror.
In spite of ten years of effort, Kronmiller was never able to gain control of the People's Coalition and put through his own radical agenda. After the victory of Gallivan's own protégé Albert Merriman in 1908, a bitter Kronmiller referred to Merriman's tenure in office as "the fifth term of King Ezra Gallivan."