Bad weather delayed the closing time of the Maryland presidential primary, state elections chief Linda Lamone said Tuesday.
Maryland has extended voting statewide for 90 minutes -- until 9:30 p.m. (0230 GMT Wednesday).
"It's gridlock," Lamone said after receiving court approval to keep the polls open.
"I mean, people can't get anywhere, especially in the central part of the state."
In Maryland, 70 Democratic national convention delegates and 37 Republican delegates are at stake.
In Virginia and Washington D.C., the other two races of the Feb. 12 "Potomac Primary," voting has already ended.
On the Democratic side, Illinois Senator Barack Obama was projected by the media to be the winner of the two contests, adding to his momentum against opponent New York Senator Hillary Clinton.
U.S. Republican presidential hopeful John McCain of Azirona and his only challenger Mike Huckabee, a former governor from Arkansas, fought neck-and-neck in Tuesday's Virginia primary.
In Washington D.C., the Republican race was too early to estimate.