The Trump campaign named the Washington Post in a libel suit on Tuesday over two articles the paper published last year claiming that the campaign tried to conspire with Russia.

The first article, published June 13, asserted that the campaign ‘tried to conspire with’ a ‘sweeping and systematic’ Russian attack on the American electoral system, while a second article published on June 20 questioned ‘who knows what sort of aid Russia and North Korea will give to the Trump campaign, now that he has invited them to offer their assistance?’

The lawyers for the Trump campaign note in the suit that special...