Democrats sued the Georgia state election board on Monday, arguing that measures approved by the board this month seeking to alter the election certification process in the state were illegal and could create chaos on Election Day.

The lawsuit claims that the board intended to give local election officials a broad license to “hunt for purported election irregularities of any kind, potentially delaying certification and displacing longstanding (and court-supervised) processes for addressing fraud.”

The lawsuit was filed in state court by local election officials, political candidates, the Democratic National Committee and the Democratic Party of Georgia with support from Vice President Kamala Harris’s presidential campaign. The move comes weeks after the state election board voted 3-2 to pass rules to give election officials authority to conduct “reasonable inquiry” into elections before certification and to require that county election officials be given “all election related documentation” before certification. Both rules, the lawsuit argues, create the impression that local election officials have discretionary power over certifying election results.

The political spotlight has pivoted back to Georgia in recent weeks, since President Biden withdrew from the presidential race and polls have shown Ms. Harris closing the gap with former President Donald J. Trump in the critical swing state. The increasingly close nature of the race there has thrust the actions of the state election board to center stage.

Members of the board who voted to pass the new rules said that they would not permit officials to ignore deadlines for certification set by state law. But the lawsuit notes that some local election officials in Georgia have already sought to delay or refuse certification, and that the new measures add to a legal uncertainty that undermines the entire election process across the state.

“These novel requirements introduce substantial uncertainty in the postelection process and — if interpreted as their drafters have suggested — invite chaos by establishing new processes at odds with existing statutory duties,” the lawsuit argues.