Former Vice President Mike Pence has raised a paltry $1.2 million for his presidential campaign, according to two campaign aides, a sum that raises dire questions about Republicans’ appetite for Mr. Pence in 2024.

Now Mr. Pence’s campaign is fighting to qualify for the first televised Republican presidential debate next month in Milwaukee. An aide said he had not yet received donations from 40,000 donors, the threshold required to make the debate stage.

Mr. Pence, who entered the race on June 5, was always a long-shot candidate in a contest dominated by his onetime running mate, former President Donald J. Trump. Adding to Mr. Pence’s challenges, he is also competing against other candidates, such as Senator Tim Scott of South Carolina, who appeal to evangelical voters.

Mr. Pence’s repeated defense of his actions to certify Mr. Trump’s defeat before Congress on Jan. 6, 2021, has alienated him from Mr. Trump’s loyal base without appearing to win many converts from the wing of the Republican Party that wants to move on from the former president.

Unlike other candidates who have employed online gimmicks to secure 40,000 donors, Mr. Pence has invested little in seeking out contributors on the internet. His campaign has spent just $14,230 in advertising on Facebook and Google, according to data collected by Bully Pulpit Interactive, a marketing and communications agency, a figure that is one-fortieth of what has been spent on those platforms by Vivek Ramaswamy, a political newcomer who joined the race in February.

In an admission of its struggle to raise money online, the Pence campaign plans to spend a large bulk of what it has raised on a robust direct-mail program aimed at helping him accrue enough donors to qualify for the first debate.

The super PAC supporting Mr. Pence, Committed to America, had raised an additional $2.7 million during the fund-raising reporting period that ended June 30, an aide said. For a fund-raising vehicle that can accept unlimited contributions, such a total is quite small.

Other Republican presidential candidates have announced far larger fund-raising sums from the three-month reporting period; some of them, unlike Mr. Pence, were in the race for the entire quarter.

Mr. Trump said his campaign and his joint fund-raising committee had raised $35 million in the second quarter. Gov. Ron DeSantis of Florida announced he had raised about $20 million. Nikki Haley, the former South Carolina governor and United Nations ambassador, raised $4.3 million for her campaign and an additional $3 million for her affiliated committees. Senator Tim Scott of South Carolina said his campaign had raised $6.1 million.

Even Gov. Doug Burgum of North Dakota, who is largely self-funding his own hopeful campaign that began the same day as Mr. Pence’s, said on Friday that he had raised $1.6 million from donors, in addition to $10 million of his own money he has given to his campaign.

Mr. Burgum has been using gimmicks like offering $20 gift cards to the first 50,000 people to donate at least $1 to his campaign, or the chance to win a Yeti cooler for a low-dollar donation, all in the hopes of making the debate stage.