PHILADELPHIA — Democrats pounced on the Republican convention in Cleveland for portraying a dark, violence-ridden nation that was coming apart at the seams. They promised that at their convention, speakers would paint a much sunnier portrait of America as it grows into the 21st century.

Ultimately, however, Democratic speakers portrayed two different Americas. One was an America that had overcome deep economic problems and achieved great progress toward a more tolerant society, and whose best days are ahead. But the other America was one in which the economic and political system is still rigged in favor of the wealthy and powerful, where workers struggle to make ends meet and put their children through college.