There was a time, not so long ago, when those wearied and horrified by the presidency of Donald J. Trump could almost convince themselves that the man was gone.

He was ostensibly a movement leader in exile, simmering in Florida, his flailing election lies confined to private monologues and modest platforms. He was no longer appearing on Fox News, the most powerful media organ of the right. His screeds on Truth Social did not land with the force of their tweeted predecessors. Even as a declared presidential candidate for the past 14 months, Mr. Trump often ceded the campaign trail to his rivals (who mostly fought one another, instead of him), skipping debates and appearing only episodically at public engagements that were not matters of the courts.

But with his landslide victory in Iowa, codifying his double-fisted hold on wide swaths of the Republican electorate, two conclusions were inescapable by Tuesday morning.

Mr. Trump is back as the dominant figure in American political life — destined again to be ubiquitous, his entwined legal and electoral dramas set to shadow the nation’s consequential year.