It was 23 years ago next month that I was proud to author the very first piece of legislation President Bill Clinton signed into law. It was the Family and Medical Leave Act (FMLA), which has allowed more than 150 million Americans take up 12 weeks of unpaid leave for the care of a loved one without fear of losing their jobs.

Even before she became First Lady, Hillary Clinton was on the front lines of this fight, not only working to make sure the FMLA passed, but working to improve it. As it turned out, Hillary was just getting started, and she has continued this fight for her entire career.

In the face of a ruthless campaign against her by the health insurance and pharmaceutical industries, Hillary fought for universal coverage as First Lady.

When Congress refused to pass her Health Care Reform proposal, Hillary was undeterred by the set back and worked across party lines to pass the Children’s Health Insurance Program, which today covers more than eight million children. My good friend, Senator Ted Kennedy, said that if it had not been for Hillary Clinton, this life saving program would not exist.

I could not agree more.

Working with Senator Hillary Clinton on the Senate Health Committee, I was inspired by her leadership in authoring the Pediatric Research Equity Act, a law that requires pharmaceutical companies to study and label the effects of their products in children — information that has improved the health of millions of children.

Hillary’s vision of an America where everyone has health insurance came back into focus with the election of Barack Obama. Her prior efforts and experience guided our drafting and passing the Affordable Care Act (ACA), a law that remains one of the proudest efforts of my congressional career.

Thanks to the ACA, no one will ever again be denied coverage for a pre-existing condition. Insurance companies can no longer charge women more, simply because of their gender, and young adults are now able to stay on their parents’ plans until age 26. Most importantly, 18 million of our fellow Americans now have health insurance coverage for the first time.

I was involved at every step of the process to pass the ACA, and I do not think it is possible to overstate how challenging it was to enact this landmark legislative victory.

And in the years since the passage of the ACA, the Republican Leadership in Congress has been relentless in their quest to repeal this important law, voting 62 times to try and roll back the progress we have made. Just recently, the sixty-third time was a charm, and the Republican-led Congress finally sent a bill repealing the ACA to President Obama’s desk, which he quickly vetoed.

But that is why who we choose as our next president is so important. His or her veto pen may be all that stands in the way of the ACA’s opponents. As President, Hillary Clinton will continue to hold the line, protecting our hard won progress with bottles of extra veto ink at the ready.

Hillary has already put forward an ambitious plan to build on the ACA, moving it toward universal coverage. She has called on Republican governors to expand Medicaid; she will make coverage more affordable with relief from premiums and deductibles; and she will crack down on excessively high prices by allowing Medicare to negotiate with drug companies.

Hillary’s plan will help millions more afford health insurance coverage. That is the outcome she has always worked for, and it is the right approach for pressing this fight forward.

I have worked with Senator Sanders. I don’t question his intentions and I admire his passion on this issue. But rather than building on the coverage that millions of Americans now rely on, his health care proposal could very well disrupt those protections and endanger the ACA.

But a presidential candidate must offer more than passion and good intentions. I spent my political life fighting alongside many progressives to improve the American health care system. In our view, the ACA is a long sought historic achievement. Let us not abandon it, or divert our party’s attention, especially when the universal health care we have fought for is becoming a reality.

Putting aside the fact that many progressive experts are asking whether Senator Sander’s plan is workable, with some questioning if his plan would raise enough tax revenue to pay for its costs, there is also a failure to appreciate how hard it was to reach this critical point.

We barely passed the ACA at a time when Democrats controlled both houses of Congress. If anyone believes the entrenched anti-ACA interests fought hard then, just wait until eliminating the entire private health insurance industry is on the table.

From the first moment I met her, Hillary Clinton has always been a fighter for what’s possible, and then keeps going. So in this Democratic primary, let us help her defend what has taken generations to accomplish.

This election is not a choice between a candidate reaching for the moon, and a candidate willing to settle for less. Both Bernie Sanders and Hillary Clinton are determined to make progress on health care, but only Hillary Clinton has a plan that accomplishes that goal.