Polling places in Baltimore failed to open on time. Election workers were unfamiliar with procedures, and ballot mix-ups put the outcome of contests in question.
The year was 1970. The historic election that sent Maryland's first African-American congressman, Parren J. Mitchell, to Washington was fraught with problems — problems strikingly similar to the irregularities revealed in the weeks since the city's April 26 primary this year.
A half-century ago, the botched primary led to the deployment of police to supervise the general election, an unprecedented decision to order a second round of voting in eight precincts and a congressional investigation.
It is unclear what might come of this year's primary after the Maryland State Board of Elections decertified the results Thursday and began combing through the data from each of the city's nearly 300 precincts.
Former Mayor Sheila Dixon has conceded the Democratic nomination for mayor to state Sen. Catherine E. Pugh. She said this week she would not seek a recount, despite continuing challenges by activists over alleged problems.
Roger E. Hartley, dean of the College of Public Affairs at the University of Baltimore, said recurring problems in Baltimore elections over decades breed distrust in the electoral system and can cause voter apathy.
"It says we're not learning from our mistakes," Hartley said. "If we're experiencing problems over and over again, and not anticipating them in advance, that has a major impact on the credibility of the system."
Investigations into the 1970 primary found apparent negligence on the part of the city election board but no evidence of fraud. The city's election chief quit about a month after the contest.
That primary stands out for the magnitude of the problems, but it is not the only example of election trouble in the city.
The city board was criticized for shutting down operations around 2 a.m. after the 1990 primary, suspending the unofficial count and leaving several races undecided.
In 2006, the state introduced an all-electronic touch-screen voting system. Gene M. Raynor, the local elections director, quit in frustration that year after a series of problems, such as equipment that abruptly turned off and election judges who failed to show up for work.
The state board intervened then as well, ordering Baltimore and three counties to take several immediate steps, including firing election judges who had shown up late and retraining some workers.
Six years ago, then-Baltimore State's Attorney Patricia C. Jessamy alleged that thousands of votes were not turned in, prompting an examination of the results that confirmed her defeat by challenger Gregg Bernstein.
Matthew Crenson, professor emeritus of political science at the Johns Hopkins University, said he was not surprised to see the problems from April's primary uncovered.
At issue are allegations that the wrong ballots were sent to certain precincts, election workers were ill-prepared and too few in number, and that not all polls opened on time.
What prompted the state's actions Tuesday was the discovery by city officials of 80 additional provisional ballots and a discrepancy between the number of ballots cast and the number of voters who checked in at the precincts.
"State intervention in Baltimore City elections is nothing new," Crenson said. "It goes back well over 100 years."
In the 1870s, Crenson said, a group of machine Democrats sneaked into the basement of a courthouse where ballot boxes were stored and burned some in the furnace to alter the election outcome.
Given the perennial nature of election problems, Crenson said, the city should undertake a careful examination of the entire system. He said officials should look for trouble spots, such as precincts with chronic problems or how to address the fact that new and short-term workers are prone to mistakes.
Public pressure, Crenson said, could force the scrutiny necessary.
"Maybe now they'll finally get it straight, one hopes," he said.
Baltimore Sun librarian Paul McCardell contributed to this article.