Alexander Burns

A hasty effort to make peace between Donald Trump and Republican Party leaders veered toward the point of collapse Friday as Jeb Bush announced that he would not back Trump in the general election and Trump unleashed a caustic personal attack on a prominent senator who declined to endorse his campaign.

The Democratic presidential race has grown increasingly bitter and personal ahead of next week’s New York primary, and Thursday night’s debate in Brooklyn may be the clearest indication yet of how fractious the contest has become.

The story is getting familiar: Donald Trump won the biggest contests of the night, as Sen. Ted Cruz of Texas captured the most conservative state up for grabs. Hillary Clinton kept a clear upper hand in the Democratic race, but Sen. Bernie Sanders of Vermont proved he would not be driven away anytime soon.

A divided Republican Party erupted into open and bitter warfare on Thursday as its two previous presidential nominees delivered an extraordinary rebuke of its current front-runner, Donald J. Trump, warning that his election could put the United States and its democratic system in peril.

If Trump’s merciless methods have seemed to help him so far, there could be a political downside over the long run. Several people he has targeted have said they would have difficulty supporting him in a general election.

Donald Trump has snatched three straight victories, built a powerful lead in national polls and knocked several opponents out of the 2016 presidential race. His path to the Republican nomination looks wider than ever. But it could still contain pitfalls and roadblocks.

Donald Trump has snatched three straight victories, built a powerful lead in national polls and knocked several opponents out of the 2016 presidential race. His path to the Republican nomination looks wider than ever. But it could still contain pitfalls and roadblocks.

Donald Trump won the Nevada caucuses Tuesday night, gaining a third consecutive victory in an early-voting state and strengthening his position in the Republican presidential race before Super Tuesday.

On the campaign trail and beyond, there may be no larger caricature of New York City than Donald Trump.

As the race has moved to New Hampshire, its tone has quietly changed: Candidates who once vied to throw the hardest rhetorical punch are campaigning in gentler terms, emphasizing their compassion and human frailty, and especially their concern for women and families.

Emboldened by Donald Trump’s defeat in the Iowa caucuses, conservative leaders and rival candidates for the Republican presidential nomination began to challenge him aggressively in New Hampshire on Tuesday, aiming to cut into his wide lead here and perhaps even to embarrass him by denying him victory in a second consecutive state.

Galled by Donald Trump’s dominance of the Republican field, and troubled by Hillary Clinton’s stumbles and the rise of Sen. Bernie Sanders of Vermont on the Democratic side, Michael R. Bloomberg has instructed advisers to draw up plans for an independent campaign in this year’s presidential race.

George Pataki, the former three-term governor of New York who undertook a long-shot presidential bid that failed to catch fire, withdrew from the presidential race on Tuesday.