In 2018, Culberson ran against corporate litigator Lizzie Fletcher, who prevailed out of a crowded and well-funded Democratic primary that gained national attention when supporters of Fletcher's primary runoff opponent, journalist and progressive activist Laura Moser, cried foul over the Democratic Congressional Campaign Committee's supposed preference for Fletcher over Moser in the primary. Despite this controversy, Fletcher prevailed by a comfortable margin in the primary runoff later that May. The race was one of the most closely watched in the nation that year, with Fletcher consistently outraising Culberson throughout the general election. Despite Culberson's proactive leadership in the wake of Hurricane Harvey, Fletcher defeated Culberson to become the first Democrat to represent the district since its realignment as a Houston-based seat in 1966, as the 7th became one of 43 Republican seats (over 1/6th of the Republican conference) to flip Democratic in the 2018 election. Culberson held his own in his longtime base of west Houston and Memorial,areas that have been the district's core for its entire existence in its present configuration; he'd represented much of this area for over three decades at the state and federal levels. However, Fletcher swamped him in the portions of southwest Houston that were added in the 2004 redistricting, as well as in the Hispanic-plurality Bear Creek area near the Addicks Reservoir that was heavily affected by flooding from Harvey. As a measure of how Republican this district had historically been, Fletcher was only the fourth Democrat to even garner 40 percent of the vote in the district.