ATLANTA — A federal judge on Monday ordered a delay in the certification of Georgia’s election results, citing concerns about the state’s voter registration system and the handling of provisional ballots. The decision effectively deepened the turmoil in Georgia’s campaign for governor, a still unsettled contest that has been among the most acrimonious campaigns in the nation this year.

Although the ruling by Judge Amy Totenberg of Federal District Court in Atlanta formally affected every election in Georgia for state and federal office, it reverberated most immediately and powerfully through the governor’s race, in which the Democratic candidate, Stacey Abrams, was within 21,000 votes of forcing a runoff election against Brian Kemp, the Republican nominee.

Georgia’s secretary of state, Robyn A. Crittenden, had been preparing to certify the outcome of the election as soon as Wednesday, one day after Georgia’s 159 counties were to complete their tabulations and six days before state law mandated certification. But in a 56-page ruling on Monday night, Judge Totenberg forbade Ms. Crittenden, who assumed office only last week, from certifying the results until at least Friday evening.

Judge Totenberg, who had already raised concerns about Georgia’s system of elections this year, wrote that the state’s announced timetable for a swift certification “appears to suggest the secretary’s foregoing of its responsibility to confirm the accuracy of the results prior to final certification, including the assessment of whether serious provisional balloting count issues have been consistently and properly handled.”