With unmatched hostility to the political establishment and an energy unlike anything seen before in modern American politics, Donald Trump promised swift and fundamental change on the campaign trail. After a few months on the job, though, the populist president appears pacified.

The leader of the free world stands powerless against a little lawyer in the Senate named Elizabeth MacDonough. She's not a senator. She's the Senate's unelected parliamentarian. And she's the one keeping Trump from fulfilling his promise to fully repeal Obamacare.

From her office just off the Senate floor, MacDonough serves as a sort of parliamentary umpire, interpreting the chamber's arcane and complex rules. In particular, MacDonough decides what legislation qualifies for a simple-majority shortcut called reconciliation, which allows bills dealing with deficit, taxes, or debt to pass with 51 votes instead of the regular 60.

So when the world's greatest deliberative body has a question, they pause, walk off the Senate floor, and ask MacDonough to read them the rules. She's the lawyer who decides what senators can and cannot do. She's keeper of the Senate rules or as Politico labeled her "Obamacare's little secret."

All of this is academic, boring, and dry. And most importantly, it's exactly why Trump hasn't followed through on his promise to completely gut his predecessor's marquee healthcare law. At least, that's what House Speaker Paul Ryan has been saying again and again this week.

With rolled up sleeves and a PowerPoint presentation, the Wisconsin Wonk told reporters Thursday that conservatives can't always get what they want because of MacDonough. Without mentioning her by name, the professorial looking Ryan explained that "there are only so many things you can do in [an Obamacare repeal] bill because of the Senate floor rules for reconciliation."

But Ryan's using the complexity of the rules to obscure what's possible. After winning the White House, the Senate, and the House of Representatives, Republicans could pass a reconciliation bill that repeals Obamacare lock, stock, and barrel. There'd be nothing that MacDonough could do to stop them.

That's not my wishful thinking. It's a repeal strategy laid out by Paul Winfree, the man Trump tapped to serve as his director of budget policy.

Writing for Politico Magazine before he got the job last November, Winfree observed that Republicans wimped out when they did a reconciliation trial run in 2015. They didn't go after Obamacare's underlying infrastructure of insurance regulations because they feared MacDonough would wrap their knuckles.

Pointing to the Supreme Court's decision in King v. Burwell , Winfree argued that Republicans have legal standing. The GOP can go after those insurance regulations, Winfree argues, because "they are inseparable from the [Affordable Care Act's] structure." And as a result, they can be repealed through reconciliation.

If MacDonough disagrees, the Senate can fire her.

There's no reason for a democratically-elected and unified Republican government to grovel before an unelected staffer. In fact, parliamentarians have been removed in the past for thwarting the will of the majority. The last one was Robert Dove, a parliamentarian whom Majority Leader Trent Lott fired.

And while a bipartisan group of senators vouch for MacDonough's honesty, her politics are a bit questionable. Before she took over the parliamentarian job, she started-off as an advisor in the 1999 Bush v. Gore Supreme Court Case. In a questionnaire published by her alma mater, Vermont Law School, she writes about advising Vice President Gore during his recount. "It was very exciting," she gushed, "and humbling."

What's more, after eight years MacDonough appears to have gotten comfortable with the previous administration. A quick review of her public social media accounts shows cozy photos taken with both Vice President Biden and Obama.

Does any of that prove that the parliamentarian is a deep state bureaucrat conspiring against the government? No. Does it raise questions about whether she can rule impartially? Yes. Would Trump be within his rights to ask Majority Leader Mitch McConnell to find a Republican for the job? Absolutely.

After winning an election on an Obamacare repeal mandate, there's no reason the president should allow overly complex and arcane rules to ensnare his agenda. Trump has the ability to slash and burn Obamacare. The president can live up to his campaign promise so long as he's not cowed by a little lawyer in the Senate.

Philip Wegmann is a commentary writer for the Washington Examiner.