The group had run ads early on slamming Murphy as a "liberal" and criticizing some of his votes, but has been silent since — and with the primary just two weeks away, it's unlikely they'll get involved.

Former Capitol Hill staffer Evan Feinberg (R) showed some early promise, and secured the backing of his two former bosses, Sens. Tom CoburnThomas (Tom) Allen CoburnPension insolvency crisis only grows as Congress sits on its hands Paul Ryan should realize that federal earmarks are the currency of cronyism Republicans in Congress shouldn't try to bring back earmarks MORE (R-Okla.) and Rand PaulRandal (Rand) Howard PaulOvernight Defense: Uncertainty for VA after Trump pick withdraws | Veterans groups hope for more input | Pompeo confirmed as secretary of State | Mattis defends Iran deal as Trump deadline nears Overnight Cybersecurity: DHS chief eyes new ways to bolster cyber workforce | Dems grill Diamond and Silk | Senate panel approves bill to protect Mueller | Two-thirds of agencies using email fraud tool Senate confirms Pompeo as Trump's new secretary of State MORE (R-Ky.). Both are popular with fiscal conservatives and Tea Party members. But Feinberg has struggled mightily to raise money — he'd raised less than $50,000 by the end of the year.

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"There have to be a lot of dynamics in place for us to get involved in a race. Feinberg hasn't raised much money," Chocola said. "We don’t mind being one of the larger financial supporters of a candidate but we don't want to be their finance committee. We think he's great on the issues but you have to be viable."

Murphy released a mid-February internal poll showing him with a 74 to 12 percent lead, and should be in a strong position for reelection. But he's not quite out of the woods: the Campaign for Primary Accountability, a deep-pocketed super-PAC targeting incumbents of both parties, is spending more than $200,000 in attempt to defeat him.

—This post was last updated at 6:02 p.m.