For all their “christianity”, republicans in the US are pretty hypocritical.
Jesus actually teached that everybody deserves to get fed and housed. That everybody deserves healthcare. That people should care for other people in their community. That is essentially the core principles of socialism.
Roman historians wrote about Jesus (Tacitus), also the Jewish historian Flavius Josephus. We can argue about his divinity (I am a believer) but I don’t think we can argue about his existence.
There were others but they are further in time so they may be quoting those two.