"The privacy interests of donors is widely recognized and valued. Various public policy initiatives have rightly encouraged donations to social welfare organizations, and these efforts are threatened when private information about donors is not adequately protected," the letter states.

The new letter, from Sen. Orrin HatchOrrin HatchIndustry 'surprised' by DOJ appeal in data warrant case US, South Korea can bury the trade barrier hatchet this week Time to get Trump’s new antitrust cop on the beat MORE (R-Utah) and other GOP senators, says that, by requesting the confidential donor names, the agency has set in motion a process that will result in the names being available for public viewing at the IRS when the investigated groups are approved to become a 501(c)(4).

"The IRS appears to be circumventing the statutory privacy protections that Congress has long provided donors," exposing the donors to "possible harassment," the Republicans said."The public release of private donor information exposes citizens to possible harassment and intimidation by those who oppose the goals of the charitable organization."

Republicans and Democrats on Capitol Hill have been clashing over 501(c)(4) and other tax-exempt groups, some of which are spending millions of dollars this year on election advertising. 

The IRS currently says that the primary purpose of 501(c)(4) groups should not be political, which has led some legal analysts to assert that those organizations should use less than 50 percent of their budget on political causes.  

Watchdogs argue groups are misusing the 501(c)(4) tax-exempt status to keep their donors secret as they spend millions on election ads. 

The Republican senators requested that the IRS provide the statutory authority to require donor names, the frequency of requests for the information, and which officials were involved in requesting and approving the "questions requesting donor names," among other issues.

Along with Hatch, the Republican senators who signed the letter were Mitch McConnellMitch McConnellGOP senator: Don't expect Trump to 'have your back' on healthcare vote Senate Dems step up protests ahead of ObamaCare repeal vote Johnson becomes fourth GOP senator unwilling to proceed on healthcare bill MORE (Ky.), Mike EnziMike EnziCongress needs to support the COINS Act The Hill's Whip List: Senate ObamaCare repeal bill Budget committee approves Trump's OMB deputy MORE (Wyo.), Lamar AlexanderLamar AlexanderThe Hill's Whip List: Senate ObamaCare repeal bill Trump administration pays June ObamaCare subsidies to insurers Republicans and the lost promise of local control in education MORE (Tenn.), John CornynJohn CornynSenate adds penalty for going uninsured to healthcare bill The Hill's 12:30 Report Cornyn: GOP won't delay ObamaCare repeal vote MORE (Texas), Kay Bailey Hutchison (Texas), Jon Kyl (Ariz.), Bob CorkerBob CorkerOvernight Defense: House panel unveils 6.5B defense policy bill | Bill threatens to suspend nuke treaty with Russia | Corker vows to block Gulf arms sales Corker vows to block arms sales to Gulf countries amid Qatar crisis This week: Senate races toward ObamaCare repeal vote MORE (Tenn.), Pat RobertsPat RobertsThe Hill's Whip List: Senate ObamaCare repeal bill Meet Jay Sekulow, the new face of Trump’s legal team Overnight Healthcare: Senate GOP eyes July vote on health bill MORE (Kan.), John ThuneJohn ThuneFour GOP senators will vote against taking up healthcare bill without changes Week ahead in tech: Lawmakers turn focus to self-driving cars Senate panel unveils aviation bill with consumer protections, drone fix MORE (S.D.) and Rand PaulRand PaulJohnson becomes fourth GOP senator unwilling to proceed on healthcare bill Five takeaways from the CBO score on Senate ObamaCare bill Overnight Healthcare: CBO score imperils ObamaCare repeal | Breaking down the numbers | WH hits back over score | Trump phones holdouts | Dems plan floor protest MORE (Ky.).

— Bernie Becker contributed to this report.