In a major new campaign poll from The New York Times and Siena College, former President Donald J. Trump leads President Biden in five of the six battleground states likeliest to decide the 2024 presidential race. Widespread discontent with the state of the country and growing doubts about Biden’s ability to perform his job as president threaten to unravel the diverse coalition that elected him in 2020. Nate Cohn, The Times’s chief political analyst, explains why the results are less a reflection of Trump’s growing strength than they are of Biden’s growing weaknesses.