Yes, IRS harassment blunted the Tea Party ground game
...In a new research paper, Andreas Madestam (from Stockholm University), Daniel Shoag and David Yanagizawa-Drott (both from the Harvard Kennedy School), and I set out to find out how much impact the Tea Party had on voter turnout in the 2010 election. We compared areas with high levels of Tea Party activity to otherwise similar areas with low levels of Tea Party activity, using data from the Census Bureau, the FEC, news reports, and a variety of other sources. We found that the effect was huge: the movement brought the Republican Party some 3 million-6 million additional votes in House races. That is an astonishing boost, given that all Republican House candidates combined received fewer than 45 million votes. It demonstrates conclusively how important the party's newly energized base was to its landslide victory in those elections, and how worried Democratic strategists must have been about the conservative movement's momentum.

The Tea Party movement's huge success was not the result of a few days of work by an elected official or two, but involved activists all over the country who spent the year and a half leading up to the midterm elections volunteering, organizing, donating, and rallying. Much of these grassroots activities were centered around 501(c)4s, which according to our research were an important component of the Tea Party movement and its rise.

The bottom line is that the Tea Party movement, when properly activated, can generate a huge number of votes-more votes in 2010, in fact, than the vote advantage Obama held over Romney in 2012. The data show that had the Tea Party groups continued to grow at the pace seen in 2009 and 2010, and had their effect on the 2012 vote been similar to that seen in 2010, they would have brought the Republican Party as many as 5 - 8.5 million votes compared to Obama's victory margin of 5 million.

President Obama's margin of victory in some of the key swing states was fairly small: a mere 75,000 votes separated the two contenders in Florida, for example. That is less than 25% of our estimate of what the Tea Party's impact in Florida was in 2010. Looking forward to 2012 in 2010 undermining the Tea Party's efforts there must have seemed quite appealing indeed....

...It might be purely accidental that the government targeted precisely this biggest threat to the president. It may just be that a bureaucracy dominated by liberals picked up on not-so-subtle dog whistles from its political leadership. Or, it might be that direct orders were given. In any case, it doesn't take a conspiracy theorist to note that the president's team was competent enough to recognize the threat from the Tea Party and take it seriously. The Obama campaign has made no secret of its efforts to revolutionize turnout models for the most recent campaign. Its remarkable competence turning out its own voters has been widely discussed, and it seems quite plausible that efforts to suppress the Republican vote would have been equally sophisticated....