Sarah Palin's endorsement of Donald Trump united two favorites of Republican conservatives, but it's an open question whether Palin's nod will help the billionaire front-runner.

The former Alaska governor is making known her favorite in the presidential race just two weeks before the Iowa caucuses where polls show Trump in a dead heat with U.S. Senator Ted Cruz of Texas—a candidate who benefitted from Palin's backing in his 2012 Senate race.

“I am greatly honored to receive Sarah’s endorsement,” Trump said in a news release. “She is a friend, and a high quality person whom I have great respect for. I am proud to have her support.” 

Overall, however, the former Republican vice presidential nominee has had middling success in her support for political candidates. About 52 percent of candidates she publicly endorsed won their races in 2010, while 56 percent did in 2012, according to the Washington Post.

Using media coverage, her Facebook page, her PAC website and its online archives, Bloomberg Politics also reviewed her 2014 endorsements and found her endorsees succeeded in winning office less than half the time. (Palin's political action committee, SarahPAC, did not respond to request for a complete list.)

In addition, voters in Iowa, which holds its caucuses Feb. 1, have expressed doubt over just how helpful Palin's endorsement is. A month before the 2014 midterm election, 56 percent of likely Iowa voters said that Palin's endorsement of Joni Ernst would do “more to hurt” than help her chances of winning a seat in the U.S. Senate, according to polling from Selzer & Co., which conducts Iowa polls for Bloomberg Politics. Just 30 percent said it would help. Ernst won anyway.

In that same survey, 57 percent of likely Iowa voters, of all affiliations, viewed her unfavorably, although only 16 percent of Ernst supporters said the Palin's endorsement was a “problem.”

To be sure, Palin has had some notable endorsement successes, including her nod of Cruz for U.S. Senate in 2012. The Texan shot to national prominence and is now, ironically, providing close competition for Trump in Iowa. Palin had earlier said she was likely to choose between Cruz and Trump.

Her endorsement failures, meanwhile, have often come when Palin backed candidates who challenged elected Republicans from the right in a longer-odds primary fights. One included Trump's spokeswoman, Katrina Pierson, who went up against Texas Representative Pete Sessions in 2012.

Palin's strength, however, seems to be her ability to mobilize grassroots conservatives, as well as garnering candidates some media coverage.

As conservative Iowa radio host Steve Deace, who has endorsed Cruz, told the Post“Palin matters because she’s still a rock star to the conservative grass roots. She has a combination of chutzpah and charisma that is lacking in the vast majority of GOP household names.”

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