We have worked with Hillary Clinton for 15 years (and in Kathleen's case, 25 years) and witnessed the power and depth of her convictions firsthand. We've seen her formidable work ethic, courage in the face of adversity and her dignity and clear head in crisis. We've also seen her two-fisted willingness to enter the brawl when America's principles are challenged. Her measured rhetoric, political savvy and pragmatism shield the heart of our nation's most determined and most democratic warrior.

She has been an uncompromising and loyal ally for each of us in our battles to protect the environment and to promote human rights around the world and juvenile justice in America. Hillary is a problem-solver, listening to people and then achieving solutions by changing attitudes.

Her transformational leadership was on display when she ran for the Senate seat in New York that had been held by our father, Sen. Robert F. Kennedy. She faced rabid, heavily funded attacks from the far right and the challenge of prevailing in traditionally Republican upstate New York. Traveling with her, we watched admiringly as she persuasively articulated an inspiring and unifying vision rooted in American values and history. Then, through patience, hard work, leadership and political acumen, she transformed many of those rock-solid conservative counties into solid Democratic strongholds.

We look forward to working beside her in the general election as she uses those same talents to change once rigid opinions and political affiliations across the nation.

Like our father, Hillary has devoted her life to embracing and including those on the bottom rung of society's ladder -- giving voice to the alienated and disenfranchised and working to alleviate poverty and injustice, while urging that we cannot advance ourselves as a nation by leaving our poorer brothers and sisters behind.

She's been an equally effective champion for human rights and for women's rights, a worldwide cause that will profit enormously by her elevation to the presidency. She has worked for peace in Northern Ireland and fought to bridge religious, racial and ethnic divides from Bosnia to the Middle East to South Africa. She has shown a rare understanding that American values can only be exported by moral leadership, by a strong home economy and by a detailed understanding of the history and cultural backdrops of the nations we engage.

She understands, as our current administration does not, the uses of power. The world, she says, is hungry for U.S. leadership but will not accept our bullying. She knows the difference and will reestablish America's lost prestige and moral authority.

Hillary Clinton's political career has been centered in comforting the afflicted, afflicting the comfortable and reminding Americans what it means to be American. As a young lawyer, she focused on children's issues and legal aid. As first lady of Arkansas, she brought healthcare to rural areas and helped reform the state's lagging education system.

As first lady, she courageously took on healthcare reform. When a massive propaganda campaign by Big Pharma and the radical right derailed her efforts, she didn't give up. She helped create the nationally acclaimed Children's Health Insurance Program. That kind of persistence in pursuit of our highest ideals is the brand of leadership America now requires. Inspirational leadership comes in many forms.

Seldom has history confronted America with such daunting challenges: a catastrophic foreign policy that has cost us our international leadership and aggravated the threat of terror; a misbegotten war that is squandering precious American lives and treasure; a healthcare system that leaves millions of Americans without coverage; irresponsible corporate power that is corroding our democracy and outsourcing our jobs, aggravating global warming and other environmental crises and reducing our economy to shambles.

We need a leader who is battle-tested, resilient and sure-footed on the shifting landscapes of domestic and foreign policy. Hillary Clinton will move our country forward while promoting its noblest ideals.

Kathleen Kennedy Townsend is the former lieutenant governor of Maryland, Robert F. Kennedy Jr. is an environmental advocate and Kerry Kennedy is a human rights activist.