Lisa Lerer

The party’s nominees lead in Michigan and New Hampshire but the Republican incumbent is ahead in Maine, according to New York Times/Siena polls of the three battlegrounds.

The dissent reflects growing unease about the party’s prospects in November, as the G.O.P. struggles to overcome the president’s unpopularity.

Senator Dan Sullivan of Alaska has shown quiet support for President Trump’s tariffs. His brother, the head of their family business, has described the economic volatility as an enormous challenge.

At an unusual midterm gathering, President Trump and his allies painted Democrats as dangerously un-American.

A string of primary wins by progressive candidates has revealed the strength of a high-energy insurgent movement but also its possible limitations.

Mr. Little, a former mayor and state senator, beat two other candidates. He focused on promises of banning corporate money from politics and supporting Medicare for all.

In an upset, Luke Bronin, the former mayor of Hartford, won the Democratic nomination, capitalizing on calls for generational change.

Senator Bernie Sanders warned that corporations have already lost control of technology that could cause “potentially cataclysmic results” for millions of people.

Abdul El-Sayed’s Senate candidacy poses a critical challenge for Democrats’ ascendant progressive wing: Can an insurgent candidate, with unabashedly liberal positions, win a general election in a moderate state?

Senator Susan Collins, who supports abortion rights, endorsed Brett Kavanaugh’s nomination for the Supreme Court. It has emerged as a major issue in her campaign for re-election.