Complex sentence: European immigrants, who came in great numbers during the latter half of the nineteenth century, were drawn into one or the other party; both parties had liberal and conservative wings, so the social and political views of newcomers could be reconciled with either.
Split into simpler sentences: European immigrants, who came in great numbers during the latter half of the nineteenth century, were drawn into one or the other party. Both parties had liberal and conservative wings, so the social and political views of newcomers could be reconciled with either.