Longtime Hillary Clinton aide Huma Abedin appeared on Capitol Hill on Friday to testify before the House Select Benghazi Committee investigating the 2012 attack that killed four Americans.
Abedin, who worked with Clinton at the State Department and is now vice chairwoman of her presidential campaign, is meeting with investigators behind closed doors.
Clinton and her allies said the investigation is politically motivated after House Majority Leader Kevin McCarthy linked Clinton's dropping poll numbers to the committee's work.
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Hillary Clinton aide Huma Abedin
Clinton aide Huma Abedin appears before Benghazi committee
Political aide Huma Abedin arrives for the "Glamour Women of the Year Awards" in the Manhattan borough of New York November 9, 2015. REUTERS/Carlo Allegri
Mayorial candidate Anthony Weiner and his wife Huma Abedin campaigning on W. 111 St. (Photo by Andrew Savulich/NY Daily News via Getty Images)
NEW YORK, NY - FEBRUARY 11: Huma Abedin and Anthony Weiner attend the 2015 amfAR New York Gala at Cipriani Wall Street on February 11, 2015 in New York City. (Photo by Larry Busacca/Getty Images)
US Democratic presidential candidate Senator Hillary Clinton (D-NY) (R) walks with her traveling chief-of-staff Huma Abedin as they approach a group of police officers after cancelling a rally in Fort Worth, Texas February 22, 2008. A Dallas police officer was killed Friday when his motorcycle struck a pillar as he was escorting democratic presidential candidate Senator Clinton to a rally in Dallas. Clinton cancelled the rally in Forth Worth, saying it would be inappropriate to hold a rally in light of the tragic circumstances. REUTERS/Jessica Rinaldi (UNITED STATES) US PRESIDENTIAL ELECTION CAMPAIGN 2008 (USA)
COLUMBIA, SOUTH CAROLINA - MAY 27: Staffer Huma Abedin helps former Secretary of State Hillary Clinton decide what special treats to buy at Main Street Bakery in Columbia, South Carolina, Wednesday, May 27, 2015. Secretary Clinton left with around dozen cupcakes. (Photo by Melina Mara/The Washington Post via Getty Images)
NEW YORK, NY - JANUARY 09: Huma Abedin attends Ryan Piers Williams' 'Monsters And Landscapes' Exhibition - Opening Reception at The Garfield Building on January 9, 2015 in New York City. (Photo by Desiree Navarro/WireImage)
Huma Abedin attends 'The Beguiled' screening in New York City, U.S. June 22, 2017. REUTERS/Brendan McDermid
Metropolitan Museum of Art Costume Institute Gala - Rei Kawakubo/Comme des Garcons: Art of the In-Between - Arrivals - New York City, U.S. - 01/05/17 - Huma Abedin. REUTERS/Lucas Jackson
Top aide Huma Abedin (C), and Senior Policy Advisor Jake Sullivan (R) listen to U.S. Democratic presidential nominee Hillary Clinton (not pictured) at her concession speech to President-elect Donald Trump in New York, U.S.. November 9, 2016. REUTERS/Brian Snyder
New York mayoral candidate Anthony Weiner and his wife Huma Abedin attend a news conference in New York, U.S. on July 23, 2013. REUTERS/Eric Thayer/File Photo
U.S. Democratic presidential nominee Hillary Clinton talks to staff members, including aide Huma Abedin (L), onboard her campaign plane in White Plains, New York, U.S. October 28, 2016. REUTERS/Brian Snyder TPX IMAGES OF THE DAY
Huma Abedin, aide to U.S. Democratic presidential candidate Hillary Clinton, looks on as Clinton makes a campaign stop to greet picketing Verizon workers who are out on strike in the Manhattan borough of New York April 13, 2016. REUTERS/Mike Segar
NEW YORK, NY - AUGUST 15: Rory Tahari (L) and Huma Abedin attend the 'Crown Heights' New York premiere at Metrograph on August 15, 2017 in New York City. (Photo by Dia Dipasupil/Getty Images)
NEW YORK, NY - AUGUST 15: Actor/producer Nnamdi Asomugha and Huma Abedin attend the 'Crown Heights' New York premiere at The Metrograph on August 15, 2017 in New York City. (Photo by Gary Gershoff/WireImage)
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"It is a partisan vehicle, as admitted by the House Republican majority leader, Mr. McCarthy, to drive down my poll numbers," Clinton said during the first Democratic presidential debate on Tuesday.
Clinton spokesman Nick Merrill said it is unclear why the committee has asked Abedin to testify "given her lack of knowledge about the events surrounding Benghazi."
Republicans contend that a number of publicly released emails between Abedin and Clinton about Benghazi, along with her role as the deputy chief of staff at the State Department during the September 2012 attacks, more than justify her testimony.
Clinton will testify before the panel next Thursday in a public hearing.
Click through to see more from Clinton's 2016 campaign:
Hillary Clinton's 2016 campaign
Clinton aide Huma Abedin appears before Benghazi committee
BALTIMORE, MD - APRIL 10: Democratic presidential candidate Hillary Clinton holds a campaign rally at City Garage April 10, 2016 in Baltimore, Maryland. Voters will head to polling places for Maryland's presidential primary April 26. (Photo by Chip Somodevilla/Getty Images)
Democratic U.S. presidential candidate Hillary Clinton laughs as she listens to Representative Steve Israel (D-NY) speak on a gun control panel in Port Washington, New York April 11, 2016. REUTERS/Lucas Jackson
NEW YORK, NY - APRIL 09: Democratic presidential candidate Hillary Clinton holds a Latino organizing event on April 9, 2016 while campaigning in the Brooklyn Borough of New York City. The New York Democratic primary is scheduled for April 19th. (Photo by Andrew Renneisen/Getty Images)
SPRINGFIELD, MA - FEBRUARY 29: Democratic presidential candidate former Secretary of State Hillary Clinton speaks during a 'Get Out The Vote' rally at the Lyman & Merrie Wood Museum of Springfield History on February 29, 2016 in Springfield, Massachusetts. Hillary Clinton is campaigning in Massachusetts and Virginia ahead of Super Tuesday. (Photo by Justin Sullivan/Getty Images)
BOSTON, MA - Former Secretary of State Hillary Clinton speaks to supporters at the Old South Meeting Hall during a rally in Boston, Massachusetts on Monday February 29, 2016. (Photo by Melina Mara/The Washington Post via Getty Images)
MINNEAPOLIS, MN - MARCH 01: Democratic presidential candidate former Secretary of State Hillary Clinton greets patrons at Mapps Coffee on March 1, 2016 in Minneapolis, Minnesota. Hillary Clinton is campaigning in Minnesota as Super Tuesday voting takes place in 12 states. (Photo by Justin Sullivan/Getty Images)
MOUNT VERNON, IOWA - OCTOBER 7: Former Secretary of State Hillary Clinton speaks to voters during an outdoor town hall meeting at Cornell College in Mount Vernon, Iowa on Wednesday October 7, 2015. (Photo by Melina Mara/The Washington Post via Getty Images)
MUSCATINE, IOWA - OCTOBER 6: Former Secretary of State Hillary Clinton speaks to a voter before leaving a farm in Muscatine, Iowa on Tuesday October 6, 2015. (Photo by Melina Mara/The Washington Post via Getty Images)
MANCHESTER, NH - OCTOBER 05: Democratic presidential candidate Hillary Rodham Clinton holds a town hall meeting at the Manchester Community College on October 5, 2015 in Manchester, New Hampshire. Clinton spoke about the need for gun control on the wake of a mass shooting at another community college in Oregon. (Photo by Alfredo Sosa/The Christian Science Monitor via Getty Images)
DAVIE, FL - OCTOBER 02: Democratic presidential candidate Hillary Clinton speaks about gun control during her campaign stop at the Broward College Ã Hugh Adams Central Campus on October 2, 2015 in Davie, Florida. Hillary Clinton continues to campaign for the nomination of the Democratic Party as their presidential candidate. (Photo by Joe Raedle/Getty Images)
WASHINGTON, DC - SEPTEMBER 19: Hillary Clinton attends the Phoenix Awards Dinner at the 45th Annual Legislative Black Caucus Foundation Conference at Walter E. Washington Convention Center on September 19, 2015 in Washington, DC. (Photo by Earl Gibson III/Getty Images)
MANCHESTER, NH - SEPTEMBER 19: Democratic presidential candidate Hillary Clinton claps on stage during the New Hampshire Democratic Party Convention at the Verizon Wireless Center on September 19, 2015 in Manchester, New Hampshire. Challenger for the democratic vote Sen. Bernie Sanders (I-VT) has been gaining ground on Clinton in Iowa and New Hampshire. (Photo by Scott Eisen/Getty Images)
PORTLAND, ME - SEPTEMBER 18: Hillary Clinton brings her Democratic presidential campaign to Maine for the first time, speaking at King Middle School. Clinton is welcomed as she is introduced at the event. (Photo by Derek Davis/Portland Press Herald via Getty Images)
CEDAR RAPIDS, IA - SEPTEMBER 7: Democratic Presidential hopeful Hillary Clinton takes time to meet supporters and take photos at the Annual Hawkeye Labor Council AFL-CIO Labor Day picnic on September 7, 2015 at Hawkeye Downs in Cedar Rapids, Iowa. Clinton spent a busy Labor Day weekend in Iowa, meeting supporters throughout the state while trying to maintain a lead over Bernie Sanders for the Democratic nomination. (Photo by David Greedy/Getty Images)
US Democratic presidential candidate Hillary Clinton takes part in a discussion after speaking about the Iran nuclear deal at the Brookings Institution in Washington, DC, on September 9, 2015. Clinton expressed firm support for the nuclear accord with Iran, calling it flawed but still strong. Clinton added that the agreement must be strictly enforced and said that if elected president next year, she would not hesitate to use military force if Iran fails to live up to its word and tries to develop a bomb. AFP PHOTO/NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
PORTSMOUTH, NH - SEPTEMBER 5: Democratic presidential candidate Hillary Clinton and U.S. Senator Jeanne Shaheen take an off the schedule stop in the River Run Bookstore before shaking hands with onlookers on September 5, 2015 in Portsmouth, New Hampshire. (Photos by Charles Ommanney/The Washington Post via Getty Images)
PORTSMOUTH, NH - SEPTEMBER 5: Democratic Presidential candidate Hillary Clinton receives an endorsement from U.S. Senator Jeanne Shaheen (D-NH) September 5, 2015 in Portsmouth, New Hampshire. Clinton attended a Women for Hillary event at Portsmouth High School. (Photo by Darren McCollester/Getty Images)
PORTSMOUTH, NH - SEPTEMBER 5: Democratic Presidential candidate Hillary Clinton walks downtown Portsmouth and takes pictures with people September 5, 2015 in Portsmouth, New Hampshire. Clinton attended a Women for Hillary event at Portsmouth High School earlier in the day and received an endorsement from U.S. Senator Jeanne Shaheen (D-NH). (Photo by Darren McCollester/Getty Images)
LAS VEGAS, NEVADA - AUGUST 18: Former Secretary of State Hillary Clinton answers questions from journalists after speaking to north Las Vegas voters at a town hall meeting in Las Vegas, on Tuesday, August 18, 2015. The former Secretary was answering questions about emails sent and received a private server system, now in question, while she was the Secretary of State. (Photo by Melina Mara/The Washington Post via Getty Images)
UNITED STATES - August 15: Democratic presidential candidate Hillary Rodham Clinton greets fairgoers as she tours the Iowa State Fair in Des Moines, Iowa, on Saturday, August 15, 2015. (Photo By Al Drago/CQ Roll Call)
CARROLL, IA - JULY 26: Democratic presidential hopeful and former Secretary of State Hillary Clinton speaks to guests gathered for a house party on July 26, 2015 in Carroll, Iowa. Although Clinton leads all other Democratic contenders, a recent poll had her trailing several of the Republican candidates in Iowa. (Photo by Scott Olson/Getty Images)
CHICAGO, IL - MAY 20: Democratic presidential hopeful and former Secretary of State Hillary Clinton arrives for a meeting with parents and child care workers at the Center for New Horizons on May 20, 2015 in Chicago, Illinois. Clinton arrived in Chicago after campaigning Monday and Tuesday in Iowa. (Photo by Scott Olson/Getty Images)
LAS VEGAS, NV - MAY 05: Democratic presidential candidate and former U.S. Secretary of State Hillary Clinton (C) poses with students and faculty after speaking at Rancho High School on May 5, 2015 in Las Vegas, Nevada. Clinton said that any immigration reform would need to include a path to 'full and equal citizenship.' (Photo by Ethan Miller/Getty Images)
NEW YORK, NY - APRIL 23: Hillary Rodham Clinton (L) and actress Maggie Gyllenhaal attend the 2015 DVF Awards at United Nations on April 23, 2015 in New York City. (Photo by Michael Stewart/FilmMagic)
NEW YORK, NY - APRIL 29: Democratic presidential hopeful and former Secretary of State Hillary Clinton speaks during the David N. Dinkins Leadership and Public Policy Forum at Columbia University April 29, 2015 in New York City. Clinton addressed the unrest in Baltimore, called for police body cameras and a reform to sentencing. (Photo by Kevin Hagen/Getty Images)
Hillary Clinton announced her campaign for president on Sunday April, 12, 2015 with a video on YouTube.