THEDA SKOCPOL produces consistently interesting work that makes many other political scientists (and most journalists, for that matter) look shallow by comparison. In 2011 she co-wrote a book about the Tea Party in which she identified some of the things that would later propel Donald Trump to the Republican nomination. At the time, most people understood the Tea Party to be a libertarian revolt against big government. Employing a radical method, which involved asking a large number of Tea Partiers what they actually thought, Ms Skocpol and her co-author discovered that this was not the case.

The folks who showed up to Tea Party meetings were not acolytes of Ayn Rand or Ron Paul. They were in fact very keen on public spending, so long as it was directed to people they thought had earned it. These Tea Partiers seldom made straightforwardly racist remarks, and probably thought of themselves as without racial prejudice. But their attitudes to government had a racial tinge, because most of the people who they thought deserved government help were people like them, which is to say white. Fast forward five years and along came a Republican candidate promising to preserve Medicare and Social Security, cut taxes and build a wall to keep out Hispanics. A movement had found its leader.

Since President Donald Trump's election, Ms Skocpol has been working on a new project. Together with her husband, she has been making repeat visits to eight counties in North Carolina, Wisconsin, Ohio and Pennsylvania to talk to novice activists drawn into politics by a desire to oppose Mr Trump. Along with Lara Putnam, a history professor at the University of Pittsburgh, she has written up some preliminary findings in Democracy. If Ms Skocpol is right about these new activists, as she was about the Tea Party, her findings will prove important.

That lots of Democrats have been energised by Mr Trump is not news. The women's marches drew huge crowds. So many people want to run that Democrats are struggling with an unfamiliar problem of over-crowded congressional primaries. Democratic candidates look to have a significant edge in small donations. In 2009, the year before a terrible mid-term year for Democrats, almost half of their candidates faced challengers who had raised at least $100,000. Half might not sound a lot, but bear in mind that only a small fraction of congressional districts are truly competitive. In 2017 the picture was a mirror image of 2009. Nearly half of Republican congressmen are facing challengers who have already raised at least $100,000 (h/t Dave Wasserman at Cook Political).

What we don't really know for sure is what sort of views these newly energised Democrats have. The answer to that question matters quite a lot. Are the newbies all Bernie Bros, hell bent on bringing single-payer health care and turning the Democrats into the congressional wing of the Black Lives Matter movement? If so, then your blogger submits that they will not necessarily do much for the Democratic Party's chances of removing Mr Trump from office, either via impeachment (which seems really unlikely) or the ballot box.

In fact, Ms Skocpol and Ms Putnam find that the new activists are a rather moderate bunch. Unlike Momentum, the movement that supports Labour's Jeremy Corbyn in Britain, they do not want to sweep away capitalism and replace it with something more just. They are disproportionately female: about 70% of the participants and most of the leadership of local Indivisible outposts are women, according to the authors. "The metropolitan advocates to whom the national media turn to explain the 'newly energised grassroots' at times exaggerate the left-progressive focus of the activists underway and overestimate their own importance in coordinating it," Ms Skocpol and Ms Putnam write. "This will not look like a far-left reinvention of Tea Partiers or a continuation of Bernie 2016. It will look like retired librarians rolling their eyes at the present state of affairs, and then taking charge." Any political movement that promises to give more power to librarians is OK with your blogger.

One result of all this, the authors predict, is a speeding up of the renewal in the Democratic Party. In a two-party system, opposition parties tend to eventually renew themselves while out of power. But this process can take a really long time. When President Barack Obama left office, the Democrats were by some estimates at their lowest ebb in state politics since the 1920s. "At the current pace, it seems likely that the pop-up leaders and grassroots groups of 2017 will, by 2019, have repopulated the local layer of the Democratic Party in much of the country," the authors reckon. If that were to happen, it would be an extraordinarily speedy turnaround. The next step is for this movement to find a leader that it can get behind, too.

CORRECTION: Due to a fat-finger error in the final paragraph, the first version of this story read "depopulated" where it should have read "repopulated". That has been fixed.