As the title character in “Carol,” Cate Blanchett grapples with forbidden passion in the 1950s. She plays a coolly elegant upper-middle-class wife and mother who falls for Therese (Rooney Mara), a young department store clerk in Manhattan. Although the story involves a lesbian love affair, Ms. Blanchett says the film is primarily about timeless, swoony emotions.

“There are many impediments, not the least of which is their gender,” says Ms. Blanchett, who has become an early best-actress Oscar contender for the role.

The...