When Senate incumbents lose in primaries, their colleagues take notice, because it doesn't happen very often. With Sen. Richard Lugar on the verge of losing his primary, another longtime incumbent seeking another term is determined to avoid at least one of Lugar's mistakes.

Sen. Orrin Hatch, R-Utah, who faces a challenge from former state Sen. Dan Liljenquistsigned a pledge from the conservative nonprofit groups Independent Women's Voice and American Majority Action to undo President Obama's signature health care law. IWV announced Hatch's decision late Monday.

The pledge advocates not just repeal but defunding, deauthorizing, and dismantling the act. 

The groups presented Hatch with an opportunity to sign the pledge when he announced he was running for reelection, so the timing of his decision to sign it this late in the cycle raises questions. Liljenquist has already signed the pledge.

A conservative strategist familiar with IWV's thinking said the group recently started running paid online ads pointing out that Indiana Treasurer Richard Mourdock has signed the pledge, but Lugar has not. The strategist added that the group also sent out a blast email last week to 250,000 people pointing out Lugar's refusal, though IWV has not technically endorsed in the Indiana race.

Hatch has navigated the GOP primary waters more proficiently than Lugar. If his team took notice of IWV's work in Indiana, it wouldn't be out of step with Hatch's dive to the right this year. For his own part, Hatch's campaign manager says he has no knowledge of who signed the pledge in Indiana.

"To be honest with you, I have no idea no idea who signed it and who has not signed it in Indiana," said Hatch campaign manager Dave Hansen when asked about the timing of Hatch's decision to sign the pledge. "[Hatch] has been for the repeal of Obamacare right from the beginning."

But it's another example of a moment in which Hatch has made an overt point to side with conservative outside groups, while Lugar has not.