With enormous thanks to ace IDer Reynolds for another fabulous find, this is the Glen Check Blazer, Trousers, and Skirt.
The Vice President-elect has worn the ensemble for several years. The jacket and skirt are a blend of wool/viscose/silk/cotton/elastane, featuring a plaid pattern in grey and white with red accents.
Here you can just see the skirt in a photo of Ms. Harris at St. Joseph AME Church in Durham, North Carolina.
The blazer is a one-button style with notch lapels, flap pockets, and a bustle-style fabric insert on the back. Below, another image of Ms. Harris at that church service in August 2019.
The skirt and trousers both have a bias-set waistband with a diagonal fabric insert in bright red, as seen below. Instead of buttons at the cuffs, the jacket uses zippers (below right).
Another view of Ms. Harris in the ensemble.
Below you see Ms. Harris in Escada’s Brikenanti Blazer (L), the Piped Tweed Jacket and Trousers (C), and the Glen Plaid Blazer (R).