The former tends to be a long term consequence of success with the latter.

But I think the mistake is to see Democrats and GOPers as party formations dedicated to liberal v conservative principles. It is closer to say that both Dems and GOPers regional coalitions that exist to promote people up the political hierarchy in a respective state or territory through the mechanism of liberal democracy. And each of these territorial members happens to have its own set of dogmatic beliefs, which inform who is eligible to climb said hierarchy.

The real formal organizational structure takes place through fundraising/media networks within a privatized network of mega-corps and donation bundlers. But this manifests as party orthodoxy, because the only way to work your way up into party leadership is to pledge yourself to the various donor/media cartels.

To say there is no Party Line or formal recruitment/organizing/promotion within these parties... Come on. You only have to look at the careers of Federalist Society Judges, Freshmen Congresscritters, and partisan rising stars to know that's not true. There's clearly a pathway to power. The people who walk it most nimbly (Kamala Harris, the Clintons, and Barack Obama are all hallmark examples of the trajectory of a successful modern Democrat) can reach the highest eschalons of authority, because they work their way through the same groups of influential mega-donors. Hell, Barack Obama did a John Kerry speed run, running through the exact same networks that set Kerry against Bush in 2004.