An extended and confrontational debate could reopen doubts about Mr. Trump’s candidacy and cast a shadow over what is supposed to be a triumphant moment of party unity.
The prospect of multiple delegate votes with unknown outcomes and unforeseeable consequences is something Mr. Trump’s campaign and Mr. Priebus are intent on preventing. What is ordinarily a carefully choreographed event — planned to conform neatly to the prime-time schedules of the television networks — could slip into chaos.
Still, the chance that Mr. Trump’s opponents could muster enough support to deny him the nomination is remote. The biggest hazard that Mr. Trump and the leaders of the Republican National Committee are trying to contain is how messy the process could become — and how much damage Mr. Trump’s campaign could sustain.
Starting on Thursday morning, delegates will begin to debate a series of proposals to change the party’s rules. Those proposed changes could include a provision that would allow delegates to vote their consciences in selecting the Republican presidential nominee, instead of voting in accordance with the outcomes of the primaries and caucuses in their states, as most state party rules require.