Rep. Michelle Steel, a two-term incumbent in California’s 45th congressional district, conceded to Derek Tran Wednesday afternoon after a long slog of a race that is one of the nation’s closest remaining contests yet to be called.

Democrat Derek Tran has defeated Republican incumbent Michelle Steel for a House seat representing California’s Orange County and Los Angeles, NBC News projects, after a contentious race that centered on the candidates’ Asian American identities and use of aggressive anti-China messaging.

Derek Tran, a first-time Democratic candidate, has flipped a toss-up California House seat, narrowly defeating GOP Rep. Michelle Steel, who conceded on Wednesday after a protracted vote count. Tran had declared victory early this week, and currently leads by roughly 600 votes.