With just more than two weeks until the Republican National Convention opens in Cleveland, Donald J. Trump’s preparations for what is usually a polished and highly choreographed affair are looking a lot like his campaign itself: chaotic, freewheeling and unpredictable…

In fact, the convention Mr. Trump described sounded rather humdrum, at least by his standards. He promised it would be fun — but not too fun — tasteful, serious and on message. And while he dismissed recent Republican conventions as lackluster affairs, he said he would not attempt anything too loud and bold…

Mr. Trump did say he expected at least one senator to speak, Jeff Sessions of Alabama, an outspoken opponent of immigration who has been one of the New York developer’s most loyal supporters. Mr. Trump also said he would like to see Sarah Palin play a role because she endorsed him over Mr. Cruz, a point of pride for Mr. Trump…

At one point, two aides confirmed, Mr. Trump was not even aware that the event had to be held in Cleveland, a decision made almost two years ago by the Republican National Committee.