Harold was born in Urbana, Illinois. Her ethnic background is extremely varied. On her father's side, she has Greek, German and English ancestry, and on her mother's side, Native-American, and African-American ancestry.
She graduated from the University of Illinois, Phi Beta Kappa with a B.A. in political science and was a Chancellor's Scholar. In 2007, she received her J.D. from Harvard Law School, where she won best brief in the Harvard Ames Moot Court semi-final and final rounds of competition. She has worked in Chicago, Illinois, as an associate attorney at Sidley Austin LLP and at Burke, Warren, MacKay & Serritella. She currently works for Meyer Capel law firm in Champaign, Illinois.
She became Miss America 2003 on September 21, 2002 (as Miss Illinois 2002). Her official platform was "Preventing Youth Violence and Bullying: Protect Yourself, Respect Yourself." Her platform choice grew out of personal experience; she recounts having been the subject of racial and sexual harassment while growing up. In a May 2, 2003 speech, Harold said when she turned to teachers and school administrators, her concerns were dismissed. As part of her platform, she became a national spokesperson for Fight Crime: Invest in Kids, a national advocacy group.
In the first week of her reign, she also adopted a secondary platform for sexual abstinence. Some pageant observers accused her of harboring a hidden agenda. The Washington Times suggested that pageant officials demonstrated a liberal bias when they allowed Miss America 1998 Kate Shindle, whose platform was HIV prevention, to advocate condom distribution and needle exchange during her time as Miss America. On October 8, 2002, Harold gave a speech at the National Press Club in Washington during which she stated that she would talk about sexual abstinence and that she "will not be bullied" into dropping the topic from her platform. Thirty-eight members of Congress sent her a letter of support, encouraging her to press on with her “healthy message of abstinence until marriage.”
During her time as Miss America, Harold interacted with legislators and testified before Congress on bullying and abstinence, which provided her with additional motivation to pursue a political career.
Harold is a Republican, and was the Youth Director for the Republican primary campaign of Illinois gubernatorial candidate Patrick O'Malley. She later served as a delegate to the 2004 Republican National Convention. She gave a speech to the convention on August 31, 2004 to support George W. Bush's faith-based initiatives. She worked on the Bush campaign to reach out to minority voters.
In May 2012, Harold was one of four finalists for the Republican nomination for Congress in Illinois's 13th district, a nomination selected by the Republican chairmen of the 14 counties covered by the 13th Congressional District, instead of a primary election. The Republican chairmen selected Rodney L. Davis, over Harold, and Davis was subsequently elected to Congress, in an expensive race.
On June 4, 2013, Harold announced she would run against Rep. Rodney L. Davis, R-Ill. in the 2014 Republican primary for Illinois's 13th congressional district. Davis, Harold's opponent in the primary, is a top target for the Democrats in 2014. On March 18, 2014, Harold lost the Republican primary to Davis 54%–41%.
On August 15, 2017, Harold announced that she would seek the Republican nomination to be Illinois attorney general in March 2018.