As a pair of Republican-controlled House panels hold hearings this week on the Internal Revenue Service, including the agency’s efforts to regulate political spending by non-profit groups, newly available documents show a broad range of right-leaning organizations weighing in to oppose the agency’s proposed rules. These comments — all negative — suggest that the latest IRS effort is a continuation of the agency’s decision, which made headlines and drew reprimands last year, to scrutinize Tea Party groups.

“These new IRS regulations against Conservative, Patriot, TeaParty Groups are Criminal,” wrote one commenter. “Leave Us Alone!”

A new analysis based on text of available comments filed with the IRS by Sunlight’s Docket Wrench tool now shows evidence that more groups — including FreedomWorks, the American Family Association and the Homeschool Legal Defense Association — have rallied their grassroots bases with alerts. Last week, Sunlight reported that Numbers USA, a group pushing for restrictive immigration policies, and True the Vote, which dedicates itself to watchdogging election fraud, were behind large groups of comments that criticize the proposals. Overall, the agency reports receiving more than 21,000 comments to date; however, the text of the vast majority of these letters became available for analysis online only in the last several days.

In this January release and video from FreedomWorks, a Tea Party group, urges its members to oppose the proposed IRS regulations: “The number of comments matters,” says president Matt Kibbe. But the video does not give any suggested language, making comments difficult to track. However, Docket Wrench shows that a small group of commenters listed FreedomWorks as their organization; likely many more were inspired by the alert. FreedomWorks operates a 501(c)4 advocacy group, which is not required to reveal its donors. While their identity remains secret, we do know something about their size: In 2012, the group received nearly 60 percent of its $15 million in revenues from just four donors, according to a report by OpenSecrets. There is also the FreedomWorks super PAC, which spent $847,000; all of its independent expenditures went to Senate races, supporting Republicans and opposing Democrats. In 2012, Sunlight broke the news that two mysterious companies gave more than half of the funding — about $12 million — for the super PAC that year.

This alert by the American Family Association (AFA), a conservative Christian group, has inspired more than 3,600 comments. Common language includes: “This provision of the proposal has nothing to do with accountability for election spending. It will however reduce the Administration’s accountability to the public.” In its alert, the AFA also states: “Many, including AFA, believe these rules are an attempt to shut down conservative organizations like AFA, Family Research Council, Concerned Women for America and the Tea Party.” Founded in 1977 by Donald E. Wildmon, a minister, the group operates more than 200 radio stations nationwide as well as online news outlets. The group is organized as a 501(c)3 charitable organization under the tax code and is therefore not required to reveal its donors.

Another cluster of comments of more than 1,600 include common language with this alert by the Home School Legal Defense Association (HSLDA), a 501(c)4 advocacy organization. “With this proposed rule…the IRS—and our federal government—has taken the position that it is against public policy for organizations to communicate with their membership and the public about what government is doing. If this proposed rule is finalized, countless organizations will be unable to tell their members what the government is doing, and how they can make a difference.” The group is not required to report its donors; however, in 2012, Politico’s Ken Vogel wrote that home-schooled high schoolers organized by the group, possibly funded under the direction of a Koch operative, helped canvas in the Wisconsin gubernatorial recall election. The group also maintains a lobbying presence on Capitol Hill, where it has lobbied for a constitutional amendment explicitly giving parents rights to direct their children’s education.

A House Ways and Means subcommittee is holding a hearing on Wednesday where members will question IRS Commissioner John Koskinen on “a variety of issues facing the IRS,” including the proposed regulations. He will also be questioned about “IRS’ targeting of certain tax-exempt organizations,” as well as the agency’s responsibilities under Obamacare. Meanwhile, House Ways and Means Committee Chairman Dave Camp, R-Mich., has ordered the Treasury Department to turn over all documents related to the proposed regulations on political nonprofits. Another hearing, planned for Thursday before a subcommittee of the House Oversight and Government Reform Committee, will focus exclusively on the administration’s investigation of IRS targeting of conservative groups.

It was last May that the IRS inspector general released a report charging that the agency had targeted conservative groups inappropriately about their political activity. Subsequently, it was revealed that liberal groups also faced additional scrutiny. The inspector general said that the agency had withheld documents about targeting of the liberal groups. On Sunday, President Barack Obama told Fox News that the IRS’ targeting of conservative groups resulted from “bone-headed decisions,” and that there was “not even a smidgen of corruption.” The Justice Department is currently investigating the allegations. The agency refused to send representatives to Thursday’s hearing before the House Oversight subcommittee, citing the ongoing investigation. House Republicans have criticized the lead investigator, Barbara Bosserman, because she has donated money to Obama.

Not all opposition against the rules comes from the right wing. The Alliance for Justice, which provides technical assistance to progressive nonprofit groups doing advocacy work, is critical of the proposed regulations and plans to comment on them. Conservative attorney Cleta Mitchell, who is helping organize the opposition, told Sunlight last week that she hopes to prepare “strange bedfellow” joint comments from conservative and liberal groups.

Sunlight has long advocated that the IRS needs to clarify rules about political activity by nonprofit groups. “An update to the IRS’s rules on the political activities of social welfare organizations i long over due,” wrote Sunlight’s lobbyist, Lisa Rosenberg last November, when the agency released the proposed regulations. “Both parties are playing the dark money game, taking advantage of lax rules around social welfare organizations to hide political spending.” Sunlight plans to submit comments on the proposed regulations, which it supports with some qualifications.

During the 2012 election cycle, the Sunlight Foundation tabulated at least $305 million in spending by nonprofit groups, a figure that in all likelihood vastly understates the actual amount because election and tax laws exempt nonprofits from reporting many of their campaign-related expenditures.

The due date for comments on the IRS proposed regulation is February 27.