President Trump greets the crowd at a rally in Billings, Mont., on Thursday. (Kevin Lamarque/Reuters)

In August, after former Minnesota governor Tim Pawlenty lost his state’s Republican primary for governor, he wistfully concluded, “The Republican Party has shifted. It is the era of Trump, and I’m just not a Trump-like politician.” Indeed, despite the protests of “Never Trump” Republicans over the last three years, President Trump is clearly at the center of the party and no longer an “outsider” or interloper.

But Trump did not make this happen singlehandedly. In our new book “Reactionary Republicanism: How the Tea Party in the House Paved the Way for Trump’s Victory,” we argue that one important group blazed the path Trump followed: the tea party movement. In substance and style, Trump has realized the agenda that tea party Republicans forged in the Obama years.

Our research focuses on tea party Republicans in the House — where the tea party’s congressional base was most powerful. We assessed each House member’s association with the tea party based on support from tea party activists and groups and whether the member explicitly identified with the tea party movement.

What distinguished tea party Republicans in the House was not their views on fiscal issues, but their views on social and racial issues. House members most aligned with the tea party were more socially and racially conservative than other Republicans. In this way, tea party Republicans in the House resembled rank-and-file members of the tea party movement.

The same is true of Trump. Although during the presidential campaign he took quite unorthodox positions on fiscal issues — defending entitlement programs and suggesting that he would raise taxes on the wealthy — as president he has instead instituted a tax cut that would benefit the wealthy and also proposed large cuts to government spending. Now he does not appear that distinct from the “Taxed Enough Already” party and the GOP generally. Conservative views on fiscal issues are not what distinguishes Trump.

Instead, it is social and racial issues. For example, House tea party members were more likely than other House Republicans to take conservative positions on abortion rights and employer-mandated coverage for contraception — not unlike the conservative position Trump has taken on these issues as well as other social issues such as LGBT rights.

Tea partyers tended to take more conservative positions on issues such as the defunding of Deferred Action for Childhood Arrivals, opposition to funding for “sanctuary cities” and support for federal contracting with corporations that violated the Fair Labor Standards Act. Likewise, Trump’s rhetoric and policies on civil rights and immigration match the views of tea party Republicans. Trump’s conservative positions on immigration — from the construction of the border wall to the revitalization of ICE — and his strong support for stronger voter identification laws resemble the conservatism of tea party Republicans, even as other Republicans stop short of endorsing Trump’s rhetoric about immigrants or policies like family separation.

The tea party and Trump resemble each other not only in substance, but in style and rhetoric. Trump is, of course, famously combative. In particular, his attacks on opponents and “digital shouting” has produced countless analyses of how he uses Twitter.

Here again, House tea party members were not much different. We analyzed the official Twitter accounts of House Republicans during the 113th Congress and found that tea party Republicans use uncivil, hyperbolic rhetoric more often than other House Republicans. Of course, Trump’s incivility — on and off Twitter — predated the rise of the tea party. But the tea party’s own incivility arguably prepared the GOP for a candidate like Trump.

There is at least one other similarity. Trump’s campaign was predicated on a gloomy portrait of life in this country. In his inaugural address, he famously spoke of “American carnage.” This same theme was also present among tea party legislators. They were more likely than other House Republicans to describe an America in decline, one in which Americans had experienced losses at the hands of a failing, and even abusive federal government led by President Barack Obama, and one in which even the American way of life was under threat, including from Muslims and undocumented immigrants.

Of course, Trump and the tea party do not resemble each other in every respect. For example, a subset of tea party members — including Justin Amash and other members who have been associated with the House Liberty Caucus — have criticized Trump or at least resisted aspects of his agenda. Moreover, our research does not suggest that the tea party caused Trump’s rise or that Trump was intentionally emulating the tea party.

But the similarities are clear. Tea party Republicans attempted to tap into and aggravate feelings of resentment toward perceived undeserving others — and this is reflected in their rhetoric and roll call votes. It is now reflected in the behavior of Trump himself.

Bryan T. Gervais is assistant professor in the department of political science and geography at the University of Texas at San Antonio.

Irwin L. Morris is professor and chair of the department of government and politics at the University of Maryland, College Park.