Passing legislation is always a difficult, messy task. America’s highly polarized political environment, with party activists demanding ideological purity on both sides of the aisle, makes that task even harder.

The announcement by Senators Mike Lee and Jerry Moran that they would oppose bringing the Better Care Reconciliation Act to the Senate floor has derailed Republican attempts to replace the Affordable Care Act.

During his campaign, Donald Trump claimed that passing health care reform would be “so easy.” So why were Republicans unable to pass a health care law despite controlling both the White House and Congress?

It turns out that the relationship between Congress and the president is more complicated than Trump thought. Most citizens and political scientists assumed that conservative Republicans would prefer any health care law that Trump supported over the Obamacare status quo.

However, my research shows that this assumption is too simplistic. As Trump now knows, ideological extremists may also vote against bills proposed by their party’s president. The recent struggle to pass a Republican health care law is a prominent example of this phenomenon.

Trump’s two-sided task

President Trump, House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell are waging a legislative battle on two fronts with no compromise in sight. Both moderate Republicans and extremely conservative Republicans oppose the current health care bill for completely separate reasons.

Moderate Republicans are concerned about how Medicaid cuts and changes to Obamacare regulations, like guaranteed essential health benefits and protections for people with preexisting conditions, will affect their constituents. On the other hand, extremely conservative Republicans want to both remove those Obamacare regulations and repeal all Obamacare taxes. This puts Republicans leaders in a bind. Anything they do to please moderates will tend to alienate the extreme conservatives, and vice versa.

The House passed the American Health Care Act thanks to support from extremely conservative members who switched their votes to support the bill. This may explain why Majority Leader McConnell’s strategy seemed more focused on winning conservative support than moderate support. The major change to the most recent version of the health care bill was the Cruz Amendment, which would allow insurance companies to offer low-cost plans that provide coverage that is much less than the standards set by Obamacare. Yet this bill did not provide funding for Planned Parenthood or protect Medicaid, two provisions that a number of moderate Republicans like Susan Collins, Shelley Moore Capito, Rob Portman and Lisa Murkowski wanted to see included.

The president’s strategy seemed to focus on conservatives as well. The list of senators invited to the White House on July 17 to solidify support for the bill included a number of conservative senators and almost no moderates.

Moving down the agenda

After the original bill’s failure, both Trump and McConnell wanted the Senate to vote on a bill to completely repeal the Affordable Care Act after a two-year delay. This gambit was essentially Republican leadership playing chicken in two ways.

First, leadership dared rank-and-file Republicans to vote against a repeal bill because most Republicans campaigned on the premise that the ACA should be repealed. However, doing so could potentially create chaos in the health care market.

Second, if Congress failed to pass a replacement health care bill within the next two years, chaos would ensue. Congress often gives itself such incentives in order to promote compromise. The major problem with this tactic is that Republican leadership would still have to find a way to placate both moderates and extreme conservatives, and potentially Democrats as well. While legislative compromise used to be a regular occurrence, it is becoming rarer in recent times due to increased polarization. Legislative productivity is near an all-time low.

The August 2011 budget deal is the last major example of Congress creating a potentially negative situation in order to incentivize cooperation. The bill created the “sequester,” which threatened to cut government spending across the board beginning in 2013 if Congress was unable to come to an agreement by that date. The idea was that neither Democrats nor Republicans wanted that to happen, so they would be forced to make a deal. While the sequester was intended to bridge differences between the two parties, a repeal and delay plan would be intended to bring Republican moderates and extreme conservatives to the bargaining table.

The trouble is that the sequester gambit failed miserably. While Congress made some small deals on both military and social spending, the 2011 sequestration agreement is still largely in effect. It looms over budget policy today. Democrats and Republicans still refuse to compromise on most budgetary issues. Republicans run the risk of the same thing occurring with health care policy if they decide to fully repeal the Affordable Care Act without a replacement in place.

In order to repeal and replace Obamacare, Republicans needed to strike a deal that pleased both moderates and conservatives. It seems unlikely that such a deal exists.

The big question moving forward is whether such a deal is possible on taxes, infrastructure, the border wall and other major parts of President Trump’s legislative agenda. In my opinion, tax reform is the item that is most likely to become law. But Republicans’ failure on health care could foreshadow an inability to bridge the moderate-conservative divide on other major issues as well.

Patrick T. Hickey does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.