This comes as a surprise, perhaps to Mike Enzi more than anyone. Liz Cheney, who started an intramural feud in the Wyoming GOP and then another within her family, has decided not to run against Enzi for the Republican nomination to the US Senate after all:

Liz Cheney, whose upstart bid to unseat Wyoming Sen. Mike Enzi sparked a round of warfare in the Republican Party and even within her own family, is dropping out of the Senate primary, sources told CNN late Sunday.

Cheney, the eldest daughter of former Vice President Dick Cheney, began telling associates of her decision over the weekend and could make an official announcement about the race as early as Monday.

Charlie Spiering reports for the Washington Examiner that Cheney has made it official:

“Serious health issues have recently arisen in our family, and under the circumstances, I have decided to discontinue my campaign. My children and their futures were the motivation for our campaign and their health and well-being will always be my overriding priority,” Cheney said in a statement.

Cheney was already facing an uphill fight against Enzi, but her decision might be based on more than just politics. Her father, former Vice President Dick Cheney, had a heart transplant in 2012, and she had a very public dispute with her sister, Mary, a lesbian, over the issue of gay marriage.

True, but the former Vice President had already had his heart transplant by the time Liz Cheney announced her bid. The fight with her sister Mary had already been fought in public, too. If those were the hurdles, Cheney had already vaulted past them. This statement seems to suggest that other health issues have arisen that are more directly related to Cheney or her nuclear family.

Perhaps it’s just as well. This campaign always seemed a bit ill-considered. Enzi didn’t have a particularly RINO-ish reputation until Cheney decided to go after him; the American Conservative Union (which hosts CPAC in March) rated Enzi at 92.73% for 2012, 89% in 2011, and 96% in 2010. On top of that, questions immediately arose as to Cheney’s connection to Wyoming, where she had lived sparingly at best for the last several years.  The sudden exit makes the decision to challenge Enzi even more questionable.

The big question now will be whether the intraparty rift in Wyoming will heal, and what this does for the credibility of groups that lined up behind Cheney against Enzi. That may depend on whether they quietly switch to supporting the incumbent in an otherwise safe seat, or attempt to push another primary opponent instead.