June 27 (Reuters) - MSNBC said on Monday that journalist Alex Wagner would take over as anchor of the 9 p.m. weekday slot four days a week, succeeding Rachel Maddow in one of the news network's most crucial roles.

Wagner, who rejoined the network in February after co-hosting shows in the early 2010s, will start in the role on August 16 and her program would air Tuesdays through Fridays.

She will also contribute to special coverage for MSNBC including the midterm elections this fall, according to a company statement.

Maddow will continue to host her eponymous show on Mondays at 9 p.m. (Reporting by Yuvraj Malik in Bengaluru)