WASHINGTON, Oct 31 (Reuters) - Democratic Party officials sued Republican presidential candidate Donald Trump in four battleground states on Monday, seeking to shut down a poll-watching effort they said was designed to harass minority voters in the Nov. 8 election. In lawsuits filed in federal courts in Pennsylvania, Nevada, Arizona and Ohio, Democrats argued that Trump and Republican Party officials were mounting a "campaign of vigilante voter intimidation" that violated the 1965 Voting Rights Act and an 1871 law aimed at the Ku Klux Klan.