Lonegan told the Star-Ledger that his internal polling showed him with "enormous" momentum and, had he known the shutdown would've played out as it did, he wouldn't have run.

"There is no doubt in my mind or in the minds of any of my campaign staff that the shutdown cost me the election," Lonegan said.  "If I had known it was going to happen and that it was going to be handled so badly in Washington, I wouldn't have run for Senate."

He said that he had strong momentum prior to Oct. 1, but that the shutdown deflated that because of how it was handled. Public polling had shown the race tightening somewhat, but Booker never dropped below a double-digit lead, and a Sept. 30 Monmouth University survey gave the Democrat a 13-point lead over Lonegan.

Booker ultimately went on to take 55 percent of the vote, an 11-point lead on Lonegan.

The Republican said, however, that the problem with Republicans in Washington was they lost control of their message on ObamaCare.

"The Republicans in Washington fumbled it terribly and it became all about the shutdown and the debacle of Obamacare's launch was lost," he said.

And Lonegan suggested Sens. John McCainJohn Sidney McCainGOP rushes to cut ties to Moore GOP strategist: 'There needs to be a repudiation' of Roy Moore by Republicans World leaders reach agreement on trade deal without United States: report MORE (R-Ariz.) and Lindsey GrahamLindsey Olin GrahamCNN to air sexual harassment Town Hall featuring Gretchen Carlson, Anita Hill Trump wrestles with handling American enemy combatants Flake: Trump's call for DOJ to probe Democrats 'not normal' MORE (R-S.C.), two critics of the shutdown strategy, which was backed by Tea Party lawmakers as a tactic to dismantle the health care law, should get primary challengers.

They drove a stake into our heart," Lonegan said.  "That's the first time we started to see the momentum move against us. They both should be primaried for what they did."