While Ms. Warren’s ambitious plans for an expanded government role in health care and higher education will be met with skepticism by Republicans, many will support her goal of making such basic services broadly accessible, while eliminating the profiteering that has made them so expensive. Her challenge will be to convince swing voters that she can achieve better outcomes at a lower cost. That would require her administration to stand up to the lobbying interests that have defeated past efforts at reform.

But this underscores Ms. Warren’s greatest strengths: her integrity, independence and commitment to helping working families. She understands their challenges because that is how she grew up. Most voters understand that fundamental change requires a president with both the know-how and moral fortitude to recapture government for the public.

There are many fine Democratic candidates, but Ms. Warren would have strong crossover appeal. Indeed, she is more market-oriented than the incumbent president, whose economic policies rely on near-trillion-dollar budget deficits, aggressive monetary policy, more tax loopholes, and government-managed trade. Ms. Warren promises structural reforms to strengthen the long-overlooked middle class. President Trump promised that in 2016. Ms. Warren might deliver.