President Barack Obama collected more than $110,000 from employees of the Internal Revenue Service during his 2008 and 2012 campaigns -- significantly more money than any other contemporary political candidate, according to a Center for Public Integrity analysis of Federal Election Commission filings maintained by the Center for Responsive Politics.
The donations were split roughly evenly between Obama's two presidential bids.
Ahead of the 2012 election, IRS employees collectively gave Republican presidential candidate Mitt Romney about $25,000 -- less than half the amount received by Obama. For his part, Sen. John McCain, R-Ariz., the GOP's presidential nominee in 2008, collected only about $6,000 from IRS employees.
The IRS has become the center of attention following an apology Friday by Lois Lerner, director of the agency's division that oversees tax-exempt organizations, for what she acknowledged was "inappropriate" targeting of conservative nonprofits for additional scrutiny since 2010. Obama himself said on Monday that offenders in the agency needed to be held "fully accountable."
On Tuesday, a report from the Treasury Inspector General for Tax Administration said the IRS used "inappropriate criteria" when reviewing organizations seeking tax-exemption.
During the past two decades, individual employees of the agency have collectively increased their political giving, which has overwhelming benefited Democrats and liberal-leaning organizations.
Overall, rank-and-file IRS employees donated more than $840,000 to federal candidates and committees from 1989 to 2012, according to the Center's analysis. Democrats and liberal-leaning organizations received about two-thirds of this sum.
While GOP-aligned groups and candidates received the remainder, during some election cycles, such as the 2002 midterms and the 2010 midterms, Republicans and conservative-leaning organizations achieved near-parity.
The Democrats' 2004 presidential nominee, John Kerry, who is now serving as secretary of state, ranked second behind Obama and ahead of Romney among candidates to benefit from the financial largesse of IRS employees, collecting about $31,000 during his failed presidential bid.
The top organizational beneficiary of money from IRS employees is the National Treasury Employees Union, which accounted for more than $102,000 in donations. The labor union has historically supported Democratic candidates, according to the Center for Responsive Politics.
Both the Democratic National Committee and Republican National Committee have also received notable support from IRS employees, with each collecting about $45,000 over the years.
All federal employees, including those who work for the IRS, are bound by the Hatch Act, a law passed in 1939 with the intent of curbing partisan power abuses by civil servants.
The Hatch Act generally bans federal employees from engaging in political activity while on the job, including soliciting funds for candidates. But political activities during personal time that do not use government resources, such as donating or volunteering for a campaign, are typically allowed.
Federal campaign finance law requires all individuals who donate more than $200 to a political group or candidate to list their employer and occupation. These filings may understate the donations of individuals who give less than the reporting threshold or who do not clearly identify the IRS as their employer.
Nonprofits organized under Section 501(c)(4) of the U.S. tax code have flourished in the wake of the U.S. Supreme Court's Citizens United v. Federal Election Commission decision in 2010, which lifted restrictions on the types of political advertising in which these groups could engage.
During the IRS's 2012 fiscal year alone, nearly 2,800 groups sought tax-exemption under Section 501(c)(4), as the Center for Public Integrity previously reported.
This tax status permits organizations to pursue a mission of promoting "social welfare" and allows them to keep their funders secret. Groups with the primary purpose of engaging in electoral advocacy must disclosure their donors.
Reporter Ben Wieder contributed to this report.