Wendy Elizabeth Stone was born on June 21, 1960, in Worcester, Massachusetts, but grew up in a small town in New Hampshire. She was "raised as a Congregationalist in a New England Yankee family."

Long graduated from Dartmouth College and later attended Northwestern University School of Law where she served as an Editor of the Northwestern University Law Review. During her third year of law school, Long studied at Harvard Law School and was graduated with distinctions cum laude and Order of the Coif, in 1995. Long has also studied as a Publius Fellow at the Claremont Institute.

She married Arthur S. Long, an attorney with the firm of Gibson Dunn, in 1998. Long resides in New York City with her husband and their two children.

In 2005, Long helped to found the Judicial Confirmation Network (now known as the Judicial Crisis Network), where she served as chief counsel. Long has advocated for judicial restraint through media and public speaking, participated in discussion and debate on U.S. Circuit Court and U.S. Supreme Court nominations, and led public support or opposition to various judicial nominees. She supported the confirmations of Harriet Miers, Chief Justice John Roberts and Justice Samuel Alito to the Supreme Court of the United States. Long also played a prominent role in opposing the Supreme Court nomination of Justice Sonia Sotomayor. In 2007, Long became a legal advisor to Mitt Romney's presidential campaign.

Long's 2012 U.S. Senate candidacy was endorsed by National Republican Senatorial Committee chairman Senator John Cornyn, former Governor George Pataki, former Representative Rick Lazio, Representative Bob Turner, Grover Norquist, the American Conservative Union PAC, former U.N. Ambassador John Bolton, former Republican presidential candidate Steve Forbes, Laura Ingraham, Sean Hannity, The New York Post, former Conservative gubernatorial candidate Herbert London, the National Organization for Marriage, the Susan B. Anthony List, New Yorkers for Constitutional Freedoms PAC, and several current and former Republican candidates and elected officials. Long also carried the support of Phyllis Schlafly's Eagle Forum political action committee. Not all of these endorsements returned for the 2016 election.

Long lost the general election for United States Senate to Kirsten Gillibrand by 46 percentage points. Long's supporter and college friend from Dartmouth, Dinesh D'Souza, pled guilty and was sentenced in 2014 for violating the federal campaign election law by making illegal contributions to the United States Senate campaign of Wendy Long in the names of others. "D’SOUZA also admitted that he knew that what he was doing was wrong and something the law forbids," with two of the illegal donations routed through D’Souza’s mistress, Denise Joseph, and her husband, Louis Joseph. His plea agreement included dismissal of a fraud charge that could have carried a five-year prison term. The government had charged D’Souza with fraud because he caused candidate Long to file a false report with the Federal Election Commission.

In March 2016, Long announced a challenge to Chuck Schumer for his seat in the US Senate. She launched her campaign on March 3 and lost the election on November 8 by 43 percentage points.