WASHINGTON — President Donald Trump’s legal team asserted Monday that he did “absolutely nothing wrong,” urging the Senate to swiftly reject an impeachment case that it called “flimsy” and a “dangerous perversion of the Constitution.” The lawyers decried the impeachment process as rigged and insisted that abuse of power was not a crime. The brief from Trump’s lawyers, filed before arguments expected this week in the Senate impeachment trial, offered the most detailed glimpse of the lines of defense they intend to use against Democratic efforts to convict the president and oust him from office over his dealings with Ukraine.