WASHINGTON – Liz Cheney’s sudden exit from her Wyoming Senate race brought a surprise end to a high-profile campaign that touched off a bitter fight within the Republican Party as well as a public spat with her lesbian sister over gay marriage.

The daughter of former Vice President Dick Cheney cited unspecified “serious health issues” in her family rather than her uphill race to unseat three-term Republican Sen. Mike Enzi in her announcement on Monday.

“My children and their futures were the motivation for our campaign and they will always be my overriding priority,” she said in a statement. One of Cheney’s daughters has Type 1 diabetes.

Cheney, who moved with her husband and five children from Virginia to Wyoming to run for the seat, offered voters a familiar name – her father served as the state’s congressman for 10 years – but faced solid opposition from mainstream Republicans who rallied around Enzi as he fought off her challenge from within the party.

The 47-year-old Cheney – a former State Department official, founder of a Washington nonprofit organization and onetime Fox News contributor – cast herself as an outsider and the 69-year-old Enzi as a lawmaker co-opted by his years in Washington.

Her campaign, however, failed to attract the backing of the major outside conservative groups such as the Senate Conservatives Fund and Club for Growth that have endorsed challengers from the right in some other Republican primaries.

So a clash between tea party activists and establishment Republicans never materialized against the conservative and popular Enzi. He had served as Gillette, Wyo., mayor for seven years and a state legislator for 10 before his election to the U.S. Senate, and he cruised to re-election with 76 percent of the vote in 2008.

The National Republican Senatorial Committee and Wyoming’s other senator, John Barrasso, had loudly proclaimed their support for Enzi, and GOP senators from other states also stood behind their colleague. Although Cheney’s fundraising has been robust, polls showed her trailing by double digits.

In November, Cheney said she opposed gay marriage, sparking a public feud with her sister, Mary, who is a lesbian and married to a longtime companion, Heather Poe.

Mary Cheney wrote on Facebook: “Liz – this isn’t just an issue on which we disagree, you’re just wrong – and on the wrong side of history.”

Poe went farther. She wrote that Liz Cheney had always supported the lesbian couple and their two children, and “to have her say she doesn’t support our right to marry is offensive.”

The high-profile dispute led Dick Cheney and his wife, Lynne, to weigh in, saying their daughters loved each other, but “Liz has always believed in the traditional definition of marriage.”

As for the campaign against Enzi, as recently as Dec. 18, in a telephone town hall meeting, Cheney excoriated him for what she contended was his failure to take a bigger role in negotiations on the federal budget that Congress approved late last year. He voted against the final version. She also maintained that his work with the “Gang of Six” negotiators helped lead to President Barack Obama’s health care law, which he also ultimately opposed.

“People on our side confuse compromise with capitulation,” Cheney said.

The talk was more gracious on Monday.

Said Enzi after a brief conversation with Cheney: “I’ve always believed in putting family first and have tremendous respect for Liz’s decision. Her family is in our thoughts and prayers.”

As for the Senate race, he said, “I haven’t been running against anybody. I’ve been running to campaign for re-election.”

Barrasso told reporters late Monday, “I think everyone in Wyoming was surprised with the announcement.” He said he respected her decision.

In the state, the Cheney campaign led to public spats that ensnared even longtime friends.

Former Sen. Alan Simpson drew a stinging family rebuke last year over his support for Enzi. Simpson said Lynne Cheney told him to “shut up” after he refused to sign a football for Cheney’s 15-year-old granddaughter at a Wyoming fundraiser.

On Monday there were no harsh words as Simpson and his wife, Ann, called Liz Cheney.

“We had the most pleasing conversation for 15 minutes or so. We just said, ‘I’m sure it was a tough one. We just know we care about you. We’ve cared about you since you were a little gal, and we’re not going to let this destroy any friendship,” Simpson said.

“I said, ‘I love your old man. He and I did 45 years together and I’m not about to see that relationship (harmed),” Simpson said. “I said, ‘your whole family’s in our DNA,’ ”

Simpson said Liz Cheney decided at Christmas that “this is a mom thing,” and she needed to be with her family. The primary is scheduled for Aug. 19 and Republicans are expected to easily hold the seat.

Despite Cheney’s decision, Simpson and others said they believed she would return to politics.

“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,” said Tammy Hooper, chair of the Wyoming Republican Party.

This time, there were several hiccups.

Last summer, Teton County records revealed that Cheney and her husband, Philip Perry, were more than two months late paying property taxes on the $1.6 million home they’d bought in Jackson Hole in 2012.

She said the late payment resulted from a misunderstanding of the terms of closing on the home with views of the Teton Range.

The week after that, The Associated Press reported Cheney had bought a Wyoming resident fishing license despite having lived in the state for less than the required one-year minimum.

Cheney paid a $220 fine for the infraction, records showed.

Bob Loevy, a political science professor at Colorado College in Colorado Springs, recalled Cheney discussing her desire to run for elected office in Wyoming when she was a student of his in the mid-1980s.

“I know it was a longtime ambition of hers,” Loevy said. “But, looking at it as a political scientist, she was attempting a very difficult thing. No matter how great your family’s reputation may be, an incumbent senator is very difficult to beat in what is essentially a one-party area.”