"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 Grant HatchTrump to award Medal of Freedom to economist Arthur Laffer Trump gambles in push for drug import proposal Biden's role in Anita Hill hearings defended by witness not allowed to testify 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 McConnellAddison (Mitch) Mitchell McConnellOvernight Defense: Trump doubles down on claim Iran attacked tankers | Iran calls accusations 'alarming' | Top nuke official quietly left Pentagon | Pelosi vows Congress will block Saudi arms sale Overnight Defense: Trump doubles down on claim Iran attacked tankers | Iran calls accusations 'alarming' | Top nuke official quietly left Pentagon | Pelosi vows Congress will block Saudi arms sale McConnell defends Trump amid backlash: 'He gets picked at every day' MORE (Ky.), Mike EnziMichael (Mike) Bradley EnziThe Hill's Morning Report - Trump, Biden go toe-to-toe in Iowa The Hill's Morning Report - Trump, Biden go toe-to-toe in Iowa Perdue proposes cutting lawmakers' travel budgets if they miss fiscal deadlines MORE (Wyo.), Lamar AlexanderAndrew (Lamar) Lamar AlexanderTaylor Swift thanks Cory Booker for signing Equality Act petition Taylor Swift thanks Cory Booker for signing Equality Act petition Senate health panel to move forward on package to lower health costs next week MORE (Tenn.), John CornynJohn CornynTrump puts GOP in tough spot with remarks on foreign 'dirt' Trump puts GOP in tough spot with remarks on foreign 'dirt' Overnight Health Care: Pelosi to change drug-pricing plan after complaints | 2020 Democrats to attend Planned Parenthood abortion forum | House holds first major 'Medicare for All' hearing MORE (Texas), Kay Bailey Hutchison (Texas), Jon Kyl (Ariz.), Bob CorkerRobert (Bob) Phillips CorkerPress: How 'Nervous Nancy' trumped Trump Press: How 'Nervous Nancy' trumped Trump Amash gets standing ovation at first town hall after calling for Trump's impeachment MORE (Tenn.), Pat RobertsCharles (Pat) Patrick RobertsEPA exempts farms from reporting pollution tied to animal waste EPA exempts farms from reporting pollution tied to animal waste Conservatives spark threat of bloody GOP primaries MORE (Kan.), John ThuneJohn Randolph ThuneTrump's border funding comes back from the dead Public policy expert: US has become 'outlier' on immigration practices Public policy expert: US has become 'outlier' on immigration practices MORE (S.D.) and Rand PaulRandal (Rand) Howard PaulOvernight Defense: Pompeo blames Iran for oil tanker attacks | House panel approves 3B defense bill | Trump shares designs for red, white and blue Air Force One Senate rejects effort to block Trump's Qatar, Bahrain arms sales Senate rejects effort to block Trump's Qatar, Bahrain arms sales MORE (Ky.).

— Bernie Becker contributed to this report.