Well ideas on the left of the political spectrum generally demand larger more centralized governments, because it's required to implement heavy-handed government interventions; whereas, ideas on the right, traditionally, are about smaller government and therefore tend to have much less of a centralized government.

Note I say ideas here, because the reality is e.g. the republicans in the US are for the most part big government politicans despite being on the right, but that seems more a bastardization of the traditional right, which historically is about smaller government.

So generally speaking, because left wing political ideas tend to involve big government, it means that centralization is generally more extensive in left wing governments, and I would argue thus left wing governments are more liable to be autocratic.