Barack Obama cast his Democratic presidential rival Hillary Clinton on Saturday as a game-player who uses “slash and burn” tactics and will say whatever people want to hear, a sharp jab at her character in the final chapter of the pivotal Pennsylvania primary campaign.

Meanwhile, Ms Clinton implored voters to look beyond “whoop dee do” speechmaking and take a hard look at who’s got the know-how to deal with the nation’s burdens.

“I want everyone thinking,” she declared, as if to suggest those backing Obama are not. Her implication was clear: She’s substance, he’s flash.

Altogether, the campaign for Tuesday’s contest was dissolving into the sort of acrimony that makes party leaders long for the finish line, before the nominee is damaged in the fall. Obama’s criticisms were direct, while Clinton’s were oblique but unmistakable. He pressed the case against her at stop after stop, blunt words set against the bucolic backdrop of his train ride through the Pennsylvania countryside.

For her part, Clinton struck back at a new Obama ad that criticises her health care plan, telling a rally in York: “Instead of attacking the problem, he chooses to attack my solution.”

“I may not be perfect but I will always tell you what I think, and I will always tell you where I stand,” Obama told the crowd.

Then he spoke of his rival. “Senator Clinton’s argument in this campaign is you can’t change how the game is played in Washington. Her argument is the slash-and-burn, say-anything, do-anything special interest-driven politics is how it works... She has internalised a lot of the strategies, the tactics, that have made Washington such a miserable place.”