WASHINGTON — President-elect Donald J. Trump’s motives for his unorthodox call with the leader of Taiwan remain mysterious, but some Republicans are hailing his improvisational diplomacy as a refreshing break with diplomatic rituals that date to the Richard M. Nixon administration. It could lay the groundwork, they say, for a healthier relationship with China.

The question, as often with Mr. Trump, is whether he will have the discipline to see through these changes. In short, was the phone call the start of a calculated policy, or was it merely a one-off gesture that will alienate China and leave Taiwan even more isolated?

So far the messages from the Trump camp are mixed. Vice President-elect Mike Pence insisted on Sunday that people were reading too much into the conversation with President Tsai Ing-wen, and that Mr. Trump was simply accepting congratulations from the “democratically elected leader of Taiwan.” But people advising the transition say Mr. Trump knew exactly what he was doing.

Certainly, the president-elect has done nothing to defuse the tensions stirred by the call. A string of vituperative Twitter posts by Mr. Trump over the weekend on China’s trade and military policies has fanned questions about whether he wants to reset the relationship with Beijing more fundamentally.