Gen. David Petraeus' resignation and admission of an extramarital affair Friday shocked political insiders and the Twitterverse alike. Even President Obama reportedly "agonized" over Petraeus' letter of resignation for 24 hours before accepting it.

But should we really be surprised? After all, Washington has a long history of extramarital affairs, from President John F. Kennedy's rumored trysts with numerous women (including one famous celebrity) to President Bill Clinton's famed admission of infidelity and dozens of others in between. (For the record, Petraeus' reported mistress is Paula Broadwell, a Harvard researcher who co-wrote his biography.)

Here, 12 politicians who, like Petraeus, confessed to having engaged in extramarital affairs. Click through the slideshow below, than add any that we missed in the comments section.

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  • Newt Gingrich

    Former Republican presidential hopeful Newt Gingrich <a href="http://abcnews.go.com/Politics/story?id=2937633&page=1#.UJ2MMuOe9TE">publicly admitted to cheating</a> on both his first and second wives during a March 2007 radio interview. He is currently <a href="http://www.rollingstone.com/politics/blogs/national-affairs/newt-and-callista-an-affair-to-remember-20120126">married to Callista Gingrich</a>, a former House of Representatives staffer that he cheated on his second wife with in 1993.

  • Bill Clinton

    In 1998, then-President Bill Clinton <a href="http://news.bbc.co.uk/onthisday/hi/dates/stories/august/17/newsid_4537000/4537597.stm">copped to having an affair</a> with White House intern Monica Lewinsky while still married to former First Lady Hillary Clinton. The couple chose to stay together after news of the affair surfaced, and are still married today.

  • Jim McGreevey

    At a 2004 press conference, former New Jersey governor Jim McGreevey came out as gay and also admitted to having an <a href="http://www.pulitzer.org/archives/6855">"adult consensual affair with another man."</a> McGreevey <a href="http://abclocal.go.com/wpvi/story?section=news/local&id=4996164">filed for divorce</a> from Dina Matos -- his wife of seven years -- in February 2007.

  • Antonio Villaraigosa

    During a July 2007 press conference -- one month after then-wife Corina Villaraigosa <a href="http://articles.latimes.com/2007/jun/13/local/me-mayor13">filed for divorce</a> -- Los Angeles Mayor Antonio Villaraigosa <a href="http://www.dailynews.com/ci_6286125">confessed to having an affair </a>with Telemundo newscaster Mirthala Salinas. The Villaraigosas<a href="http://latimesblogs.latimes.com/lanow/2010/10/mayor-antonio-villaraigosas-divorce-is-finalized.html"> finalized their split</a> in October 2010.

  • Kwame Kilpatrick

    After lying under oath about an affair, former Detroit mayor Kwame Kilpatrick eventually <a href="http://articles.chicagotribune.com/2008-09-05/news/0809041263_1_kilpatrick-and-beatty-detroit-mercy-school-christine-beatty">admitted to cheating</a> with his former aide, Christine Beatty, in September 2008. Kilpatrick is still married to his <a href="http://www.mlive.com/news/detroit/index.ssf/2012/09/kwame_on_trial_carlita_kilpatr.html">wife, Carlita Kilpatrick</a>, whom he cheated on.

  • John Edwards

    After previously <a href="http://abcnews.go.com/Politics/video/flashback-john-edwards-denies-affair-5545530">denying infidelity accusations</a>, former North Carolina senator John Edwards finally <a href="http://www.thedailybeast.com/newsweek/2008/08/07/the-story-is-out.html">confessed to having an affair </a>with filmmaker and campaign aide Rielle Hunter in August 2008. He later revealed that he also <a href="http://today.msnbc.msn.com/id/34963767/ns/today-today_news/t/edwards-admits-fathering-child-mistress/#.UJ2Z5OOe9TE">fathered a child </a>with Hunter. Edwards and his then-wife, Elizabeth Edwards, <a href="http://articles.nydailynews.com/2010-01-28/gossip/17945614_1_elizabeth-john-edwards-love-child">separated in January 2010</a>, and she <a href="http://abcnews.go.com/Politics/elizabeth-edwards-dies-age-61-battling-breast-cancer/story?id=12319133#.UJ2afuOe9TE">died in</a> December 2010 before the divorce could be finalized.

  • John Ensign

    In June 2009, former Nevada senator <a href="http://articles.cnn.com/2009-06-16/politics/ensign.affair_1_sen-john-ensign-republican-policy-committee-affair?_s=PM:POLITICS">John Ensign revealed </a>that he had an extra-marital affair with someone who worked for him. Cynthia Hampton, an ex-campaign aide who was also married at the time, came forward and admitted that <a href="http://www.msnbc.msn.com/id/31409202/ns/politics-more_politics/t/ex-campaign-aide-ensign-admits-affair/#.UJ2eMeOe9TE">she had been involved with the senator</a>. Ensign is <a href="http://articles.latimes.com/2011/mar/08/nation/la-na-john-ensign-20110308">still married</a> to his wife, Darlene.

  • Mark Sanford

    In July 2009, former South Carolina governor <a href="http://www.huffingtonpost.com/2009/06/23/sanfords-story-questioned_n_219809.html">Mark Sanford came clean</a> about a secret affair he was having with Argentine woman, <a href="http://www.time.com/time/specials/packages/article/0,28804,1908008_1908007_1907930,00.html">María Belén Chapur</a>. Nearly six months after news of the scandal broke, his wife, <a href="http://www.cbsnews.com/2100-250_162-5966433.html">Jenny Sanford, filed for divorce</a> in December 2009.

  • Elliot Spitzer

    In March 2008, Elliot Spitzer -- who was governor of New York at the time -- admitted to being <a href="http://www.huffingtonpost.com/2008/03/10/spitzer-prostitution-scan_n_90766.html">linked to a prostitution ring</a> that was under government investigation. He was caught while making arrangements to meet up with <a href="http://www.nytimes.com/2008/03/13/nyregion/12cnd-kristen.html?_r=1&ref=nyregion&oref=slogin">prostitute Ashley Dupre</a>.

  • Arnold Schwarzenegger

    Former California governor Arnold Schwarzenegger<a href="http://www.huffingtonpost.com/2011/05/17/arnold-schwarzenegger-fathered_n_862867.html"> confessed to fathering a love child</a> with household staffer Mildred Baena in May 2011 -- just a week after he and wife of 25 years, Maria Shriver, <a href="http://www.huffingtonpost.com/2011/05/10/arnold-schwarzenegger-and_n_859774.html">announced their separation</a>. In July of that year, Shriver <a href="http://www.people.com/people/article/0,,20498160,00.html">filed for divorce</a>, but rumors of a <a href="http://www.nypost.com/p/news/national/they_re_back_uLfQyTC3ul1NMbUbvDtUQM#ixzz1nt6tUAWT">potential reconciliation</a> continue to swirl.

  • Gary Condit

    Amid a 2001 missing person scandal involving <a href="http://www.washingtonpost.com/wp-srv/metro/specials/chandra/ch1_1.html">congressional intern Chandra Levy</a>, former California congressman Gary Condit <a href="http://www.foxnews.com/story/0,2933,29029,00.html">admitted to having a romantic relationship</a> with the then-24-year-old. It was eventually determined that Condit -- who later switched gears and <a href="http://www.people.com/people/article/0,,1016589,00.html">denied the affair</a> -- was not tied to her <a href="http://www.huffingtonpost.com/2010/11/22/chandra-levy-verdict-ingm_n_786898.html">disappearance or murder.</a> Condit and wife Carolyn <a href="http://www.aolnews.com/2010/10/19/ex-congressman-linked-to-chandra-levy-writing-revealing-book/">stayed married </a>after the scandal.

  • Vito Fossella

    Former New York congressman <a href="http://articles.nydailynews.com/2008-05-01/news/17897636_1_vito-fossella-dui-bust-elderly-woman">Vito Fosella was arrested</a> in May 2008 and charged with driving under the influence. In an interesting turn of events, it was his mistress -- retired Air Force <a href="http://www.silive.com/news/index.ssf/2008/05/staten_islands_fossella_admits.html">lieutenant colonel Laura Fay</a> -- who bailed him out. In a prepared statement, <a href="http://www.silive.com/news/index.ssf/2008/05/staten_islands_fossella_admits.html">Fossella later admitted</a> that he had a relationship with Fay and that he was the father of her then-three-year-old child. Fossella and his wife, Mary Patricia Fossella, <a href="http://abcnews.go.com/Politics/anthony-weiner-thomas-jefferson-arnold-schwarzenegger-top-politicians/story?id=15395918#4" target="_hplink">remain married</a>.