Thousands of Tea Party activists will gather Monday at rallies across the nation to mark Tax Day, April 15–and to re-ignite a movement that had been written off as dormant by the media and the political classes.

After propelling the Republican Party to the majority in the House of Representatives in 2010–and likely for the next decade thereafter–the Tea Party seemed to retreat. It failed in its political aim of defeating President Barack Obama in 2012, largely because of its earlier failure to find an alternative nominee to Gov. Mitt Romney. It was tarnished unfairly as racist, extremist, and–especially after the Tuscon shooting of Jan. 2011–violent, and was blamed even by some Republicans for the debt ceiling impasse in mid-2011.

Yet the Tea Party also succeeded in stopping the rapid growth of federal spending and taxation. The Tea Party ensured that there would be no bailouts for profligate states and no large-scale tax increases. Though it had to swallow the tax increases of the “fiscal cliff” deal in the early hours of 2013, it essentially preserved 98% of the Bush-era tax cuts. And by shifting the national debate in favor of deficit reduction, the Tea Party laid the foundation for the budget sequester–a set of across-the-board spending cuts that the American public has largely tolerated, even in the face of President Obama’s attempts to create panic and outrage.

The Tea Party ought to be fading into the background. The issues that the Obama administration has placed on the national agenda–immigration, gun control, and gay marriage–are thought to be ones where the Tea Party is weakest, far from the fiscal agenda that gave it early momentum and prominence. And yet the Tea Party has new momentum as an opposition force. Without articulating clear policy positions on any of these divisive issues, the Tea Party has rallied opposition nonetheless, holding the line in Congress and the states.

The key has been the Tea Party’s continued stress on the Constitution–not just the Second Amendment, but also the fundamental principle of the rule of law, and the federalist structure that Washington has done so much in recent decades to erode. These general principles are enough of a foundation for a political stand–and broad enough to admit wide differences of opinion on the substantive underlying issues themselves.

Recent months have proved challenging for conservatives, especially as politicians once backed by the Tea Party have begun reshaping themselves as moderates–Sen. Marco Rubio (R-FL) on immigration, Sen. Pat Toomey (R-PA) on gun control, and several governors on Obamacare funding for state Medicaid expansion. Yet the Tea Party appears set for a revival–partly because of the failures of Republican national leadership, partly because of the emergence of new leaders, but largely because the country needs the opposition that it provides.

In a system there the two parties find themselves unable to undo the worst aspects of policies in which they have often colluded, and the mainstream media no longer bother to hold Washington in check, only the Tea Party seems to have the potential to provide the spark for the country’s urgent renaissance.