Marc Piscotty / Getty Images Liz Cheney pictured in July announcing her candidacy in Wyoming.

Citing “serious health issues” in her family, Liz Cheney has dropped her primary challenge against Wyoming Republican Sen. Mike Enzi, ending a bitter political contest that had spilled over into a public fight over gay marriage with her sister.

In an official statement released by her campaign,the eldest daughter of former Vice President Dick Cheney said the health of her family was her "overriding priority."

"Serious health issues have recently arisen in our family, and under the circumstances, I have decided to discontinue my campaign," the statement said.

"My children and their futures were the motivation for our campaign and their health and well being will always be my overriding priority. Phil and I want to thank the thousands of people in Wyoming and all across the country who have supported my campaign.

The daughter of former Vice President Dick Cheney said she will drop out of competition for a U.S. Senate seat from Wyoming, citing family health concerns. NBC's Kelly O'Donnell reports.

"As a mother and a patriot, I know that the work of defending freedom and protecting liberty must continue for each generation. Though this campaign stops today, my commitment to keep fighting with you and your families for the fundamental values that have made this nation and Wyoming great will never stop."

NBC News has learned through sources close to the family that the "serious health issues" cited involve Cheney's children and not her father who has a well-chronicled medical history. Cheney and husband Phil Perry have three daughters and two sons. Despite her political setbacks in this race, sources say the decision is "about real family matters" and it was "not a light decision to get in or out of the race."

Her election bid in the deeply conservative state was controversial from the outset, and Cheney struggled to win over voters within the state. A partisan poll commissioned in November showed that Cheney garnered the support of just 17 percent of likely primary voters, compared to 69 percent for Enzi, the incumbent.

"While it is not always easy, Diana and I have always believed in putting family first. We have tremendous respect for Liz's decision. She and her entire family are in our thoughts and prayers," Enzi said in a statement. "I remain as committed as always to the job the people of Wyoming have elected me to do. I look forward to continuing my campaign for re-election in the coming months."

Her Wyoming credentials were challenged in spite of her family's deep roots in the state, because she spent much of her youth and adult life in Virginia.

Last summer, she committed an embarrassing political gaffe in a state where hunting and fishing are taken very seriously by mistakenly buying the wrong fishing license after living in Wyoming for just a few months.

Then a bitter spat over same-sex marriage between the Cheney sisters spilled over into the public arena when Mary Cheney and her wife, Heather Poe, took to social media to blast the elder sister for her continued opposition to gay marriage.

The Wyoming GOP reacted in a statement: "The Wyoming Republican Party wishes the best to Liz Cheney and her family as they deal with difficult family health issues. Liz has been a stalwart supporter of our party raising hundreds of thousands of dollars for our candidates and county parties. Liz is a rising star in Wyoming and national politics and we look forward to her return when the time is right for her and her family."

NBC News' Alastair Jamieson, Kasie Hunt, Kelly O'Donnell, and Reuters contributed to this report.

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