Even absent a natural disaster, the idea that a president might shut down the government when Congress is controlled by his own party seems like madness. And yet here we are, with President Trump reaffirming earlier this week that he would consider letting the government shut down if his border wall proposal does not get funding from the Republican-controlled Congress.

The border wall, never a particularly popular policy even according to one of Trump's favorite pollsters, was nonetheless one of Trump's signature promises (though, if memory serves, the promise also included requiring Mexico – not Congress – to cough up the funding).

But the border wall isn't the only thing that divides Republicans. The ideological lines between the parties have been modestly blurred in the Trump era, and as a result some intra-party divisions have been inflamed. Republicans, once champions of free trade, are now the party more skeptical while Democrats have embraced it. With a Republican in the White House, GOP positivity toward "the federal government" is up while Democrats have grown more wary of Washington. Those holding fast to the old principles find themselves at odds with those who have adopted the new trends in their own parties, while many lingering intra-party battles over things like immigration and the environment remain.

With congressional Republicans no longer holding back as much in their criticism of Trump's actions and behavior, it feels like the divide within the Republican Party is deep. Primary challengers to incumbent Republican senators from more Trump-friendly candidates are popping up in places like Arizona and Nevada, and some anti-Trump Republican policymakers have been alleged to be contemplating 2020 primary challenges to the president himself.

Yet despite the open hostility in the party, including division between the White House and Speaker Paul Ryan over things like the pardon of Joe Arpaio and the response to Charlottesville, Va., there are things getting done. They aren't flashy or in the form of a "signature" achievement, but according to a new Pew Research Center analysis, this 115th Congress has actually been quite more productive than most people realize. Some 46 "substantive" bills will have been signed into law before Labor Day, outpacing in sheer number the bills passed and signed during former President Barack Obama's brief period of unified Democratic governance.

But Obama's opening months included some "signature" laws, such as the stimulus, (officially the American Recovery and Reinvestment Act). The lack of a signature achievement has led to the perception that Congress has not achieved much, and Republican approval of their own Congress is only around 1 in 6 Americans. And it's fair for a voter to think Congress can't get anything done when what at one time seemed like the most prominent unifying goal of Republican lawmakers – the repeal of the Affordable Care Act – has gone down in flames.

Yet, the rollback of Obamacare was always going to be harder than the easy rhetoric of repeal made it sound, given the reality of deep division within the party over the appropriate role for the federal government in providing health insurance to people.

Which brings us to tax reform.

If there is one issue where one could justifiably assume that Republicans are all in agreement, it is on lowering taxes. Republicans can't always agree on where to cut spending. They certainly can't agree on what to do about entitlements. There isn't a unified foreign policy vision, and there's no consensus on immigration reform.

But even the details of tax reform threaten to make things more complicated for the GOP. Cutting the estate tax is a political winner within the GOP, as is the idea of cutting the corporate tax rate to 15 percent. Nearly 7-in-10 Republicans support doubling the standard deduction, and two-thirds of Republicans like the idea of reducing the number of brackets.

In many ways, those are cuts by various names, not true simplifications of the tax system. The tough stuff, like removing some deductions? Only about half of Republicans like the idea of eliminating deductions even when excluding charitable interest and mortgage. And even on cuts, there are serious questions about whether even Republican voters would truly warm to the idea of reducing taxes on wealthy Americans as a part of a tax plan.

The reality is that the Republican Party may have unified government but is not unified enough on many major signature policy areas. Congress has been productive when focusing on bites of policy that don't inflame the divisions within the party and quietly do the work of governing. There may not be major headlines for things like funding NASA or repealing little-known regulations, but with Republicans so divided, the era of big bills for big issues may be on its way out.

Kristen Soltis Anderson is a columnist for the Washington Examiner and author of "The Selfie Vote."