New Historicism is a theory that argues that any text must be studied from the context of the author and the text itself - the historical forces that influenced the work must be analysed. New Historicism therefore investigates how a work of literature was influenced by the time in which it was produced.
A New Historicist often looks at the ways in which specific groups of people are marginalised in work of literature. This is where New Historicism and Marxism share some links, as Marxism is an approach that emphasises the importance of class struggle in society. Thus, an examination of a novel by Jane Austen, say, might identify that the sphere of reference is focussed upon the landed gentry alone. Combining New Historicism and Marxism would result in an approach that would explore how the working class are exluded and marginalised in her works, and also critically identify how marrying beneath oneself or below one's social sphere was frowned upon by Austen.