1. A computer-implemented method, comprising: receiving, by a computing system and at a first time, a first spoken input from a user of an electronic device, the first spoken input comprising an original utterance by the user; based on the original utterance, determining, by the computing system, a first set of character string candidates wherein each character string candidate represents the first spoken input converted to textual characters, and wherein determining the first set of character string candidates comprises using a speech recognizer to determine a first word lattice that represents the first set of character string candidates and a first set of probabilities, each probability corresponding to a character string candidate; providing, for display to the user, a selection of one or more of the character string candidates in response to receiving the first spoken input; receiving, by the computing system and at a second time, a second spoken input from the user; determining, by the computing system, that the second spoken input is a repeat utterance of the original utterance; based on determining that the second spoken input is a repeat utterance of the original utterance, and using the original utterance and the repeat utterance, determining, by the computing system, a second set of character string candidates, wherein determining the second set of character string candidates using the original utterance and the repeat utterance comprises: using the speech recognizer and the first word lattice as a language model to determine a second word lattice that represents the second set of character string candidates and a second set of probabilities, each probability corresponding to a character string candidate of the second set of character string candidates; determining an intersection or union of the first word lattice and the second word lattice and, for each character string candidate included in the intersection or union, determining a combined probability based on the probabilities from the first set of probabilities and the second set of probabilities that correspond to the character string candidate; and determining a third set of character string candidates based on the intersection or union and the determined combined probabilities.