WASHINGTON — Newly disclosed emails show Michigan Republicans angling to give their party a dominant position through gerrymandered maps and celebrating the plight of their Democratic rivals.

Republicans in the state have denied that they sought partisan gain when they drew new legislative boundaries in 2011. But a federal lawsuit, which argues the maps are unconstitutional, has unearthed records showing Republicans intent on drawing boundaries that would help their party.

The emails, disclosed in a filing on Monday, boast of concentrating “Dem garbage” into four of the five southeast Michigan districts that Democrats now control, and of packing African-Americans into a metropolitan Detroit House district. One email likened a fingerlike extension they created in one Democratic district map to an obscene gesture toward its congressman, Representative Sander M. Levin.

“Perfect. It’s giving the finger to Sandy Levin,” the author of the message wrote. “I love it.”

Excerpts from the emails were filed in United States District Court in Detroit this week as part of a battle between the plaintiffs and the defendant — formally, Michigan’s secretary of state — over how much evidence the sides must disclose before a trial begins. The emails were first reported by Bridge Magazine, run by the Center for Michigan, a public policy think tank.