They acquitted him on one, which was based on a $200,000 check that the heiress Rachel Mellon had written him in January 2008, the month he dropped out of the race for the Democratic nomination for president. The result was seen as a setback for the Justice Department’s public integrity section, the watchdog agency that has struggled to rebuild itself.

The Justice Department offered no indication on whether it would retry Mr. Edwards.

Unless it decides to do so, the verdict and mistrial end one of the most scandalous chapters in the history of presidential campaigning, weaving in a hidden child, an ambitious would-be first lady dying of cancer, secret money from ultrarich supporters and legal scrutiny of the laws that regulate how money given to candidates for office can be used.

It is unlikely that the verdict will help politicians better interpret the labyrinth of campaign finance law or lead to more gifts to candidates, said Richard L. Hasen, an expert in election law at the University of California, Irvine. “This is not going to open up a free-for-all where you’re going to have the ‘super-PAC’ billionaires giving large ‘gifts’ to their candidate friends.” He noted that the Federal Election Commission has made it clear that it looks critically upon the practice unless there has been a pattern of gift-giving unrelated to campaigns, as with Ms. Mellon to Mr. Edwards.

If he were advising candidates, he said, “I would encourage them to be extremely cautious so as not to get caught up in something which could cause an overzealous prosecutor to try to make a name for himself or herself.”

The government contended that Mr. Edwards used about $1 million to finance a complex scheme to keep Rielle Hunter, a former campaign videographer with whom he began an extramarital affair in 2006, from his wife and the public while he pursued the presidency.