American voters absorbed their first view of an extraordinary split-screen campaign this week, with President Biden sprinting across one of the country’s top battleground states and former President Donald J. Trump sitting — and appearing to snooze — in a New York courtroom.

Just as it has for years, the country’s political map has hardened into a battle across a handful of crucial swing states. Mr. Trump’s required appearance in a Lower Manhattan courtroom effectively leaves him little choice but to continue to be a weekend warrior in those states. Now, for much of the week, Mr. Biden has the electoral landscape largely to himself.

Mr. Biden campaigned across Pennsylvania, casting Mr. Trump as an out-of-touch plutocrat and collecting endorsements from the Kennedy family. In Scranton, the president’s childhood hometown, he jettisoned “Bidenomics” — the right’s derisive term for his economic policies that White House aides tried and largely failed to reclaim — in favor of arguing that voters faced a choice on the economy between “Scranton values or Mar-a-Lago values.”

Two days later, in Philadelphia, he connected the assassinations of President John F. Kennedy and Robert F. Kennedy to what he called Mr. Trump’s vision of “anger, hate, revenge and retribution” and embrace of political violence.

“Your family, the Kennedy family, has endured such violence,” Mr. Biden told several Kennedys as he accepted their support. “Denying Jan. 6 and whitewashing what happened is absolutely outrageous.”

The Pennsylvania trip was part of Mr. Biden’s shift into a more aggressive campaign stance against Mr. Trump. He has visited every battleground state since his State of the Union address in March, offering voters a retooled message that sharpens the contrast between the policies of the current president and his predecessor on a laundry list of issues, including abortion rights, democratic norms, tax policy and the economy.

The president’s attempt to transform the race into a binary choice between him and Mr. Trump — instead of a traditional re-election referendum on the incumbent — has been aided by the live play-by-play coverage of Mr. Trump’s courtroom appearances. So far, Mr. Biden and his team have been careful to say next to nothing about the trial or Mr. Trump’s other three criminal cases.

Yet the images require little narration. Campaigning across the country, Mr. Biden looks like a conventional presidential candidate. Sitting in a courtroom, Mr. Trump looks like a criminal defendant.

For months, Democratic strategists, candidates and officials privately worried that Mr. Biden’s campaign was falling short in what is widely expected to be a razor-thin contest, questioning the president’s energy levels, swing-state operations and message.