Will Club for Growth take on Murkowski?
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Sen. Lisa MurkowskiLisa Ann MurkowskiGOP warns McConnell won't blink on debt cliff Graham tries to help Trump and McConnell bury the hatchet Trump, allies launch onslaught as midterms kick into gear MORE (Alaska) has the lowest score of any GOP senator on the fiscally conservative Club for Growth's annual scorecard, a sign the deep-pocketed group may be interested in supporting a primary election challenger against her next year.

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Murkowski voted with the group's interests just 27 percent of the time in 2014, lower than any other Republican in the upper chamber. Her lifetime score is 57 percent.

The Club highlighted her ranking when it released its scorecard Monday morning, a sign it might be looking to oust her in 2016.

Tea Party favorite Joe Miller (R), who defeated Murkowski for the 2010 GOP nomination but lost to her in the general election, is said to be considering a rematch.

The Club endorsed Miller in 2010, but only after he'd beaten Murkowski in the GOP primary. Last year, the group shocked many in D.C. by backing establishment favorite and now-Sen. Dan Sullivan (R-Alaska) over Miller in their three-way primary.

Club spokesman Doug Sachtleben said Murkowski's "score speaks for itself and we're watching her 2016 race" when asked if the group might back an opponent.

Sen. Mark Kirk (R-Ill.) also scored low on the Club's rankings, at 36 percent with a 56 percent lifetime score, but the Club's president, David McIntosh, indicated earlier this year that Kirk was unlikely to be a target because of the difficulty a hard-line conservative candidate would have winning in Illinois.

Sen. Roy Blunt (R-Mo.), who is up for reelection as well, only scored 47 percent last year; he has a 71 percent lifetime ranking.

Updated at 11:15 a.m.