House Energy and Commerce Chairman Henry Waxman (D-Calif.) is known to inspire tremendous staff loyalty, and this loyalty is an essential component of his effectiveness as a lawmaker.

A loyal staff often means an experienced staff, and these aides will help the committee’s new chairman as he attempts to guide a number of health care initiatives through Congress this year.

Karen Nelson, Waxman’s senior health specialist, is one of his longest-tenured staff — she has been with him since 1978 — and a key player in his efforts to implement health care reform, a variety of her former colleagues and lobbyists say.

“All roads go through Karen” on health care, a former House Democratic aide said.

One of Waxman’s top health care priorities for this year is ensuring health care coverage for all Americans. This effort includes covering children through an expansion of the State Children’s Health Insurance Program, along with increasing federal Medicaid funding for states. Currently, Waxman is taking a leading role in moving the health care provisions of the Democrats’ economic stimulus package.

Waxman is also pushing to give the Food and Drug Administration authority to regulate tobacco products and to overhaul the FDA to strengthen its inspection of imported products.

Nelson is invaluable to Waxman as he pushes his ambitious agenda because she is seen as essentially his alter ego and has his full trust and confidence, various former aides and lobbyists said. This means the chairman does not have to be in every meeting because Nelson and other veteran staff members can confidently speak for him on any issue.

Nelson can and does take a leading role in cutting deals on legislation because of her experience. Waxman trusts her to tell him when he should have a problem with a proposal, the former Democratic aide said.

Such trust is key to quickly and efficiently moving legislation forward, especially with an issue as complicated as health care, said Jonathan Westin, assistant director for legislative affairs at United Jewish Communities.

Like a true loyal staffer, Nelson declined repeated requests to be interviewed. But her tenure and expertise brings respect on and off the Hill. Nelson is a “towering figure in health care circles around town,” another former Democratic aide said.

Bruce Lesley, president of the children’s health advocacy group First Focus, agrees. “She knows more about the collection of health care policy issues than anybody in town and, as important, knows where all the bodies are buried on each issue,” he said.

In particular, Nelson will have a leading role in the fight to expand health care coverage, either through Medicaid or SCHIP, said Ron Pollack, founding executive director of the liberal health care group Families USA.

Not only does Nelson have the knowledge of the issues, but she is strategically effective because she understands political realities, Pollack said. It is her understanding of the issues and how to work through political hurdles that has helped make Waxman one of the most effective Medicaid advocates on the Hill, he said.

But Nelson is seen as partisan and has previously done little to reach out to Republicans, a former GOP aide said. Her knowledge of policy and process make her a formidable foe.

“If you’re on the wrong side, you will get flattened,” the ex-Republican aide said.

Yet while Nelson is seen as a hard-charging advocate for Waxman and his priorities, some Republicans also view her as a straightforward, fair broker. Although Republicans sometimes accused Waxman of being hyper-partisan during his tenure as the top Democrat on the Oversight and Government Reform Committee, a Republican aide said Nelson is expected to continue to be a pleasant, knowledgeable and reliably honest opponent on various health care issues with Waxman’s new role as Energy and Commerce chairman.