Maryland’s July 19 primary features several highly competitive races. It could be days or even weeks before analysts declare winners and elections officials certify results.

“We’re used to, in most contests, knowing who the winner is when we go to bed,” said Nikki Baines Charlson, deputy administrator at the Maryland State Board of Elections.

“This election is different,” she said. “We’ve never had half a million people request a mail-in ballot.”

That unprecedented number of mail-in votes cannot begin to be counted until two days after the election, and it may take weeks for elections officials to go through them all, officials said.

Local boards will post mail-in ballot results at the end of each counting day. But it is unclear how many days each jurisdiction will need. In tight races, that could mean an excruciating wait.

Here’s what you need to know: