The tea party movement arose seemingly out of thin air in the spring of 2009 in response to Rick Santelli’s widely publicized rant attacking plans for providing financial relief to Americans who faced foreclosure on high-risk mortgages during the financial crisis. Over the next few weeks, groups sympathetic to Santelli’s message and opposed to the Obama administration’s plans to drastically increase spending on relief programs of various types and provide health insurance coverage for the uninsured sprang up around the country.

This movement was far from spontaneous, as Rachel Blum acknowledges in this brief but thoroughly researched book examining the impact of the tea party insurgency on the Republican Party. It received consistent encouragement from Fox News and other conservative media outlets and considerable financial support from the libertarian Koch Brothers network. But despite the clear evidence of “astroturfing,” Blum shows that the tea party developed into a true grassroots movement that aimed at nothing less than taking over the Republican Party and, in doing so, challenging some of the more established conservative organizations that provided crucial support in its early days. Leaders of these organizations were surprised when they discovered that tea party activists were not content to keep their focus on issues of government spending and regulation and work within the confines of existing Republican organization. But establishment conservatives were not the only ones surprised by the independence of those activists and groups—so were many liberal political commentators who initially questioned the movement’s motivations and independence.

Blum argues that the tea party movement can best be understood in the broader context of theories of party factionalism of which it represented one form—what she calls insurgent factionalism. This is a type of factionalism that aims at challenging established party leaders and, ultimately, taking over party organizations, rather than working cooperatively with established party leaders. Along these lines, Blum demonstrates that tea party activists often displayed strong mistrust of established Republican organizations and leaders and regularly supported candidates challenging those organizations and leaders in GOP primaries.

The ideological foundation for this challenge to the party establishment was what Blum and others, notably Barreto and Parker, have described as reactionary conservatism. This is a type of extreme conservative ideology that, contrary to the early branding of the tea party movement, is heavily focused on social issues, rather than government spending and regulation. What really upset tea party supporters, Blum concludes, was not deficit spending or tax increases but a general perception that the country was changing in ways that threatened the status of white Christians as the dominant group in American society—a perception that was greatly intensified by the presence of the first African American president in the White House.

As the title of the book indicates, Blum concludes that the tea party movement has faded from view in the last few years because it has largely accomplished its main objective of taking over the Republican Party. Reactionary conservatism has become the dominant ideology of the Republican Party both at the grassroots and in government. As Blum also notes, nothing shows this more clearly than the rise of Donald Trump to the leadership of the Republican Party and the presidency.

Although Trump was never directly involved in the tea party movement, his successful 2016 campaign clearly tapped into the strongly antiestablishment feelings and desire to roll back the clock on social change that fed the movement at the grassroots. Trump’s presidency has richly rewarded those who shared those sentiments while simultaneously alienating the majority of American voters who were turned off by that message of hostility to science, to immigrants, and to liberal elites.

Blum’s book provides many insights into the thinking and strategies of tea party activists based on content analyses of tea party blogs and mission statements, as well as hundreds of interviews with grassroots organizers and activists. All of this information will be useful for those interested in the history of the movement and its impact on the Republican Party. Blum’s ability to gain access to tea party leaders and activists and to understand the underlying grievances giving rise to the movement was undoubtedly aided by her personal background. In the preface to the book, which is well worth reading in its own right, Blum describes her upbringing as the child of parents deeply involved in the conservative Christian movement that preceded the rise of the tea party. Blum’s upbringing and her undergraduate education at Patrick Henry College, a conservative institution devoted to preparing students for lives of conservative activism, prepared her well to conduct the fieldwork that provided much of the qualitative data for the book.

One problem with Blum’s approach is that it sometimes risks losing sight of the forest for the trees. Although Blum does provide some discussion of earlier right-wing insurgencies such as the Goldwater movement of the 1960s, the book could benefit from closer attention to the changes in American society and culture that preceded the emergence of the tea party and paved the way for its success, as well as for the rise of Donald Trump. For example, it would be interesting to see whether there was a correlation between areas where the tea party enjoyed its greatest strength at the grassroots in 2009–12 and where Donald Trump enjoyed his greatest success in Republican primaries in 2016.

I am also a little skeptical about the utility of the “insurgent factionalism” framework proposed here for understanding intra-party conflict in general. That is because, as Blum acknowledges, there has been nothing quite comparable to the tea party on the Left. Although intra-party ideological conflict is inevitable in a two-party system, and the Democrats certainly have seen their share of that sort of conflict, the left wing has never had the level of influence within the Democratic Party that the Far Right has had within the modern Republican Party.

My own hypothesis is that this reflects a fundamental difference between the two parties in the United States. Democrats, including those on the Left, want the government to try to solve social problems by enacting major policy reforms. Republicans, especially on the Right, have no positive agenda other than cutting taxes and reversing policies enacted by Democrats. As a result, left-wing activists and members of Congress may be reluctant to attack their moderate colleagues too harshly out of fear of undermining the party’s legislative agenda, especially when Democrats are in power. That hypothesis is about to get a test during the first two years of the Biden administration.

Even though the tea party’s heyday has passed, Blum’s book provides an important and timely perspective on the rise of reactionary conservatism and the influence of right-wing extremism and activism on the modern Republican Party. For anyone who still needs convincing, Blum’s book provides plenty of evidence that the tea party movement of 2009–12 paved the way for Donald Trump’s takeover of the Republican Party in 2016. Even with Trump out of the White House, his brand of reactionary conservatism is likely to remain a powerful if not dominant influence on the Republican Party in many parts of the United States for a long time.