Brian Steinberg Senior TV EditorChristopher Isham, who has been the Washington Bureau chief at CBS News for more than a decade, will cede many of his duties to focus more intently on coverage around the 2020 election before leaving the company at the end of the year.In a memo to staffers, CBS News President Susan Zirinsky said Ingrid Ciprian-Matthews, who oversees recruitment and development at the ViacomCBS unit, will serve as an interim head of the bureau while leading the search for its next