Hours before midterm election polls were set to open, a bombshell memo revealed that incumbent Democratic Sen. Jeanne Shaheen (D-NH) was personally involved in coordinating a plot with ex-IRS official Lois Lerner and President Obama's political appointee at the IRS to illegally target conservative leaning and Tea Party not-for-profit groups during the 2012 election, according to letters exclusively obtained by The Daily Caller.

Since it was discovered that the Internal Revenue Service, under the leadership of Lerner, used their power to unfairly harass conservative nonprofit groups for tax exempt status and delayed dozens of applications for years, conservatives and some Democratic U.S. senators have repeatedly appealed for the case to be investigated, with further calls being made for the IRS to release 2012 correspondences exchanged between the IRS and Shaheen at her personal Washington office, Breitbart reported.

But apart from some tangential letters and evidence, the tax agency has largely ignored their pleas and has delayed releasing the information to a major conservative Political Action Committee after they requested it multiple times under the Freedom of Information Act, according to emails.

However Monday's published letters now hint at "some level of cooperation between the IRS and Democratic members of Congress in the lopsided scrutiny of conservative nonprofits," The Daily Caller's Patrick Howley observes.

In the memo, the Democratic senator was briefed about a coordinated IRS-Treasury Department plot to target political activity by nonprofit 501(c)(4) groups, indicating that she was a principle character in the controversial scandal.

"Shaheen got the inside info from the IRS, making it clear she was the point person in a group composed of six close Democratic colleagues including Chuck Schumer and Al Franken, who joined with Shaheen in quietly writing a letter to then-IRS commissioner Doug Shulman expressing their concern about new nonprofit groups engaging in political activity in 2012," The Daily Caller's Howley writes.

"These regulations have been in place since 1959," IRS chief counsel William J. Wilkins, a White House visitor described by insiders as "The President's Man at the IRS," personally wrote in a hand-stamped memo to "Senator Shaheen" on official Department of the Treasury letterhead on April 25, 2012.

"We will consider proposed changes in this area as we work with Tax-Exempt and Government Entities and the Treasury Department's Office of Tax Policy to identify tax issues that should be addressed" in designing new regulations and "guidance."

"The IRS is aware of the current public interest in this issue," he continued in the memo to Shaheen. "I hope this information is helpful. I am sending a similar response to your colleagues. If you have questions, please contact me or have your staff contact Cathy Barre at (202) 622-3720."

Following the bombshell report, there has been no response from Shaheen's campaign about the memo. But Michael Biundo, consultant of Citizens for a Strong New Hampshire, one of the groups targeted by the IRS, told Breitbart News that he's horrified at Monday' publication.

"Despite Citizens for a Strong New Hampshire's FOIA request, the IRS has continued to stall and illegally ignore deadline after deadline for the past several months in order to delay the release of correspondence between their office and Senator Shaheen and now we know why," Biundo said in an email. "On the eve of the midterm elections, a plot between Senator Shaheen, Lois Lerner, and President Barack Obama's political appointee at the IRS to lead a program of harassment against conservative groups aimed to trample free speech has come to light." 

"This abuse of government power should not be tolerated. Senator Shaheen should immediately release all correspondence with the IRS. Granite Staters deserve transparency and honesty from their elected officials but unfortunately, the Senator continues to hide."

"By refusing to release information between the IRS and a U.S. Senator and a Member of Congress in a timely manner in advance of next week's election, the IRS is engaging in a deliberate campaign to prevent voters from gaining important information that could have an impact on the outcome of the election," ACLJ chief counsel Jay Sekulow added.

Meanwhile, with this year's election coming down to the wire, the final days have seen Sen. Scott Brown and Shaheen engaged in a brutal election battle.

But with the release of the shocking memo late Monday, it awaits to be seen whether Brown will now race ahead in New Hampshire's election despite recent polls showing a neck-to-neck battle, Breitbart reported.