John Lewis to Clinton: 'Happy Birthday, Madame President'
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Rep. John Lewis (D-Ga.) wished former Democratic presidential nominee Hillary ClintonHillary Diane Rodham ClintonGraham: There's a 'bureaucratic coup' taking place against Trump Fox News poll shows Dems with edge ahead of midterms Poll: Democrats in position to retake the House MORE a happy birthday on Thursday in a tweet calling her "Madame President."

Lewis's tweet Thursday afternoon had been retweeted more than 1,500 times less than a half-hour after it was posted.

Clinton won the popular vote for the presidency last November, but lost the White House to President TrumpDonald John TrumpGrassley: Dems 'withheld information' on new Kavanaugh allegation Health advocates decry funding transfer over migrant children Groups plan mass walkout in support of Kavanaugh accuser MORE in the Electoral College.

Lewis, a civil rights icon, endorsed Clinton and campaigned on her behalf. His tweet followed others from fellow prominent Democrats, including Clinton's husband, former President Bill ClintonWilliam (Bill) Jefferson ClintonSexual assault is not a game — stop using women to score political points Trump, GOP regain edge in Kavanaugh battle Presidential approval: It's the economy; except when it's not MORE.

Clinton, who turned 70 on Thursday, is currently touring the country as part of a national book tour for her memoir, "What Happened." The book examines the 2016 election and Clinton's eventual defeat to Donald Trump.