Brian Steinberg Senior TV Editor Blayne Alexander is joining an exclusive club — the coterie of veteran correspondents who lead NBC News‘ long-running “Dateline.” The weekly true-crime documentary show has developed into a significant stand-alone business that comprises not only the TV program, but podcasts and a very well-watched library that fuels both re-airs on cable and streams on various digital platforms. Alexander, who is returning from maternity leave, joins a team of correspondents that includes Andrea Canning, Josh Mankiewicz, Keith Morrison, and Dennis Murphy.