Christie’s donor support appears largely organic, as he is spending less money than any other major candidate in the primary — bringing in $3.8 million in the third fundraising quarter while spending just $1.5 million. Other candidates still attempting to qualify for the debate, including South Carolina Sen. Tim Scott and North Dakota Gov. Doug Burgum, spent significantly more than Christie.

“Christie’s ability to organically earn support from voters proves his message taking on Trump is not only distinct, but works,” said Karl Rickett, campaign spokesperson.

To date, Christie’s campaign has spent just $28,300 on digital advertising and none on television, according to AdImpact. Tell It Like It Is, the super PAC supporting him, has spent $2.8 million on ads, mostly on television and streaming.

Since launching his campaign in early June, Christie, the GOP field’s most vocal critic of Trump, has given more than 200 interviews — most of which were on television, radio and podcasts, according to a campaign official. The Trump critic has been a regular on network Sunday morning shows.

Christie is polling in low single digits nationally and suffers from higher GOP unfavorability ratings than the rest of his primary opponents. But he is banking heavily on New Hampshire, where he remains competitive in the race to be the top Trump alternative. In that first primary state, he sits behind Haley, but neck and neck with DeSantis, with a polling average of 9 percent. Christie’s lean campaign operation, so far with low overhead, may help him to stay in the race longer than some of his opponents — based on their current burn rates — even if his fundraising remains modest.