Donald J. Trump, the poll leader for the last five months in the Republican presidential race, is about to find out whether he has permanently changed the rules of politics, or if some of those old standards still linger.

His long-promised “next phase” defined by new spending, such as a wave of television commercials, has so far failed to materialize, week after week. His advisers have not revealed the existence of any pollsters on their staff or any advertising team. He has no real research operation to examine his own vulnerabilities or those of his opponents and, based on Federal Election Commission filings, little in the way of a voter contact operation to identify and turn out his supporters.

Regardless of how he fares in next year’s state caucuses and primaries, Mr. Trump has established himself as a political force, pushing Republicans toward a bellicose brand of populism that will linger even if he is not their standard-bearer.

But he has conspicuously opted against spending in conventional ways that could fortify his lead or harm weak rivals, discarding the playbook that winning candidates have used for many decades.