What were some of the measures that Jefferson took to discredit Adams? How did one of these measures backfire on Jefferson?

To begin with, here is a quote from page 196;

"Adams was supposedly maneuvering to have his eldest daughter married into the family of [British King] George III in order to establish a royal bloodline. He also had purportedly arranged to smuggle a small bordello of London prostitutes across the Atlantic to satisfy his instincts for debauchery within the presidential mansion. Jefferson, for his part, was described as a demonstrable coward who had avoided military service in the Revolutionary War and had fled rather precipitously while governor of Virginia at the approach of British troops."

As for the measure that backfired........ read to the bottom.

"Jefferson and Madison published the Kentucky and Virginia Resolutions, which claimed that states had a right to nullify the Constitution over injustices like the Alien and Sedition Acts. Then, after the split between Hamilton and Adams, Jefferson and Madison fed the press anti-Federalist gossip. Jefferson commissioned the notorious scandalmonger, John Callender, to compose articles which ridiculed Adams both personally and politically.

Jefferson’s association with Callender soon turned sour when Callender was arrested under the Alien and Sedition Acts for these articles. Callender, who believed Jefferson had under-paid him, published the story of Jefferson’s affair with his slave Sally Hemings."