The U.S. Capitol. (John Kelly/The Washington Post)

In 1933, President Franklin D. Roosevelt persuaded Congress to expedite a raft of major laws to combat the Great Depression. Ever since, the end of the first 100 days has been a time to mark the accomplishments of new presidents. For President Trump, to quote an old Republican hand, the first 100 days have been the “honeymoon from hell.” By any legislative metric, little progress has been made on the president’s “100-day action plan to Make America Great Again.”

Why have Trump and the Republican Congress delivered so little? There’s a relatively quick version of the answer: Trump is historically unpopular, lacks governing experience and surrounds himself with neophyte advisers. Across town and toting his own legislative agenda, Republican House Speaker Paul D. Ryan said the GOP “has to go from being an opposition party to being a governing party.”

And although all of that is true, legislative dysfunction is deeply rooted within today’s House. The two parties are at ideological extremes, and the ruling Republicans are more divided among themselves than at any point in the past century. The combination undermines their capacity to deliver on the president’s agenda and dampens the chances for a productive Congress.

How does Trump compare with recent presidents?

Political capital is built on public support and post-election momentum — and often peaks in a president’s first few months in office. Most presidents leverage their electoral boost to push through major initiatives and proposals blocked by their predecessor. After President Bill Clinton’s rocky start, Democrats swiftly enacted a first-ever family leave law vetoed by President George H.W. Bush. The second President Bush made quick progress on a multitrillion-dollar tax cut, as well as landmark education reform. Within a month, President Barack Obama’s Democratic Congress delivered a record-size fiscal stimulus, soon followed by pay equity and children’s health reforms that President George W. Bush had vetoed.

Before and after the November election, Trump outlined a menu of ambitious offerings — including immigration and tax restructuring, infrastructure spending, trade renegotiation, his oft-emphasized southern border wall, as well as Affordable Care Act repeal and Wall Street deregulation.

The Senate has confirmed Neil M. Gorsuch as a Supreme Court justice, albeit only after nuking the need for Democratic votes. And via the Congressional Review Act, a seldom-used, fast-track law, Republicans quietly overturned more than a dozen late-term Obama rules — loosening regulatory limits on oil, gas, coal and telecom industries, among others.

Ongoing Republican efforts to repeal and replace the health-care law have been far more visible. Even with tactics designed to cut out the Democrats, House Republicans remain at odds with their Senate colleagues, the White House and one another over how to unwind an increasingly popular law, wasting precious legislative floor time in the process.

In turn, without offering any substantive proposals, Trump has bounced between advocating action on health care, taxes and infrastructure. Coincidentally, the federal spending authority expires on the eve of Trump’s 100th day in office. A government shutdown looms should Congress and the president fail to strike a budget deal this week.

This is why Republicans struggle to legislate

But the Republicans’ governing difficulties run deeper than an unpopular president backed by inexperienced advisers pursuing deeply polarizing proposals. A view inside the Capitol suggests why.

In the figure below, we use lawmakers’ ideological scores to place every House majority party since 1901 along two dimensions. (When Republicans hold the White House and Congress, the start of the Congress is marked in red; periods of unified Democratic control are marked in blue; a divided government shows up in gray.)

As you can see, the 2017 House is nearly the most polarized in more than a century. And among the years under unified Republican control, 2017 stands out as the most polarized.

The current House is unusual in another critical way. Along the Y-axis, we map each Congress based on the relative ideological breadth of the two House parties. When the score is high, it means that Republicans are more divided than their Democratic opponents. When the score is low, Republicans were the more cohesive party.

Today’s GOP House stands out in the upper-right quadrant. The parties are extremely polarized, and Republicans are far more fractured ideologically than the Democrats. That’s what we saw in the Republican stalemate over Obamacare, in which the far-right Freedom Caucus rejected anything but flat-out repeal while the moderate Tuesday Group sought improvements. Such stalemates may well recur when Republicans turn to tax restructuring and other Trump proposals. Unless Republicans can overcome their extreme internal divisions, Ryan will be challenged to corral his conference and move major legislation.

We see a more mixed bag in the Senate, as shown in the chart below. Like the House, the Senate is deeply polarized, meaning that Republicans will continue to have a hard time bringing Democrats on board. Republicans are also more divided than Democrats, but these GOP cleavages are not nearly as sharp as they are in the House. This suggests that the GOP agenda may gain more traction in the upper chamber.

Ideological disagreements between the parties surely shaped Republicans’ legislative strategy this year: Anticipating that Democrats would oppose Trump’s agenda, the GOP leaned heavily on procedures that eliminated the need to court Democratic votes.

But those tactics backfired. Yes, they enabled the GOP to quickly repeal some Obama regulations. But using the filibuster-proof budget reconciliation process highlighted internal Republican Party disagreements over how to restructure health care. It threatens to do the same for tax restructuring, as well. In other words, ironically, the GOP’s parliamentary strategy limits what Trump and Congress can achieve.

A more popular president with a more disciplined and fully staffed administration might have had more success herding these fractured Republican majorities. But Trump attracts so much popular opposition that the divided Republican majority can’t come together to make the compromises needed to legislate. As David Jones wrote here at The Monkey Cage yesterday, presidents can recover from slow legislative starts. But the road is likely to be uphill for Trump and his unruly Republican Congress.

Mark Spindel is founder and chief investment officer at Potomac River Capital, a Washington-based investment firm.

Sarah Binder and Spindel are co-authors of “The Myth of Independence: How Congress Governs the Federal Reserve,” Princeton University Press, coming this summer.