WASHINGTON — Two Democratic Party donors and a former party staff member have filed an invasion of privacy lawsuit against President Trump’s campaign and a longtime informal adviser, Roger J. Stone Jr., accusing them of conspiring in the release of hacked Democratic emails and files that exposed their personal information to the public.

The case was organized by Protect Democracy, a government watchdog group run by former Obama administration lawyers. It filed the claim just short of a deadline under a one-year statute of limitations for privacy invasion lawsuits: WikiLeaks published the first archives of stolen Democratic National Committee emails, which intelligence agencies say Russia hacked to harm Hillary Clinton’s presidential campaign and help Mr. Trump, last July 22.

Mr. Trump and his political advisers, including Mr. Stone, have repeatedly denied colluding with Russia, and the 44-page complaint, filed on Wednesday in the Federal District Court for the District of Columbia, does not contain any hard evidence that his campaign did. But it is seeking to depose witnesses and obtain campaign emails and other documents during the discovery process that is a standard part of lawsuits.

If a judge permits the case to reach that stage, the lawsuit would become a new and independent fact-finding investigation into the Trump-Russia issue — one that is overseen by a judge rather than by congressional Republicans, like the oversight inquiries conducted by the House and Senate Intelligence Committees, or by the Trump administration, like the criminal inquiry led by the special counsel, Robert S. Mueller III.