PHILADELPHIA — Democrats pushed on Friday to extend the excitement spurred by a four-day convention that culminated in the presidential nomination of Hillary Clinton, taking the fight against Donald J. Trump to the battleground states that could decide an election just over 100 days away.

Two weeks of speeches, music, infighting and ultimately mountains of balloons and confetti for Democrats and Republicans have cemented the terms of the debate and left both parties as unified as they can be. Now comes the grueling homestretch of the campaign, where advertising will step up and the bickering between the candidates is likely to become even more biting.

Signaling the importance of Pennsylvania, Mrs. Clinton and her running mate, Senator Tim Kaine of Virginia, stayed in Philadelphia to campaign early Friday, holding a rally at Temple University to begin a post-convention bus tour through Harrisburg and Pittsburgh and then Youngstown and Columbus, Ohio.

Mr. Trump made his way west for campaign events in Colorado Springs and Denver. While en route, he lashed out on Twitter at those who were critical of him at the Democratic National Convention, specifically calling out Michael R. Bloomberg, New York’s former mayor, and John R. Allen, a retired four-star general, as failures.