“We’re sorry. An application error has occurred. Goodbye.”

That’s the robotic message callers get when they dial up Donald Trump’s campaign headquarters in the battleground states of Wisconsin and Ohio. It’s the same declaration in Delaware, Indiana, Maryland, West Virginia and Oregon.

And it’s a potential symptom of a broader problem for the Trump campaign.

As Trump gets ready to officially accept the Republican presidential nomination next week in Cleveland, some are questioning whether his campaign, which largely has operated on a shoestring budget so far, can keep up with the operation and spending of the Hillary Clinton machine.

Unlike predecessors Mitt Romney and John McCain, who used their own hires in key swing states, Trump has indicated he will leave much of the team-building and organizing to the Republican National Committee and state parties.

So far, his campaign has only sent a few people to battleground states and — while Trump recently has picked up the fundraising pace — has not yet indicated it is ready to spend the big bucks on a general election race.

The latest headlines on the 2016 elections from the biggest name in politics. See Latest Coverage →

Clinton and her allies so far have outspent Trump’s campaign by a 15-to-1 margin on ads. To date, Clinton’s campaign has spent $25 million on general election advertising. Factor in money from super PACs and the total is a whopping $57 million, compared with $3.6 million for pro-Trump ads.

For their part, Trump officials voiced confidence. Campaign senior adviser Tana Goertz told FoxNews.com to expect a big ramp-up following the convention.

Trump campaign chairman Paul Manafort shook off concerns and told Fox News on Friday the campaign was getting “into a groove.”

“We really started raising money in June,” Manafort said, claiming they raised over $51 million last month. “Trump is on fire on the campaign trail. …He’s doing rallies, he’s doing town halls, he’s doing local media, he’s doing prepared speeches.”

The lack of coordination at the local level, though, has left some feeing nervous.

“Having worked in GOP grassroots politics for more than 20 years I can honestly say I have never seen a Republican presidential campaign with this weak of a field presence,” one Florida Republican told Politico. “Where are the local offices in the major cities?”

Another GOP insider added, “Donald Trump just hired a guy yesterday in Colorado. One guy — does that count as an organization?”

FoxNews.com recently tested the waters and called local headquarters in the battleground states of Florida, Colorado, Pennsylvania, Michigan, Nevada, New Hampshire, North Carolina, Virginia and Iowa.

Of those calls made to state headquarters, three went straight to voicemail. Other calls resulted in the automated error messages.

Only in New Hampshire did someone answer the phone. The volunteer on the line was very nice, said she would pass on FoxNews.com’s questions and get back soon. Twenty-four hours and two calls later — still no word.

In North Carolina, FoxNews.com left a message which was responded to in less than five minutes. But, as in New Hampshire, the callbacks promised never materialized.

The Huffington Post conducted a similar experiment earlier this month.

The publication attempted to call the contact numbers for the Trump campaign in all 50 states. According to their data, on only six occasions did someone actually answer the phone. Of those six, “several” said that a physical office would be opened only after next week’s national convention in Cleveland.

A state-by-state review conducted by The Associated Press revealed that the national GOP has not delivered the goods on its ground game, which has left local operatives from Richmond, Va. to Richmond, Calif., feeling jittery about when reinforcements will be sent in and whether the late scramble will be successful.

In the battleground state of Ohio, Republicans were told they’d have 220 paid staffers by May. In reality, only 50 were hired. Pennsylvania Republicans were promised 190 paid positions but got 60 instead. In Colorado, there are about two-dozen employees on the payroll — less than half of the 80 that should have been in place, according to the AP.

The ground game has been a persistent problem for Trump and his donors – with some wondering if it’s too little too late.

Trump didn’t actively begin soliciting funds until May. He was able to win the Republican primaries without dropping millions on advertising campaigns — instead enjoying free media exposure in the form of extensive coverage. He has expressed doubt over whether large-scale spending is even necessary.

Goertz, who works nationally for the Trump campaign as a surrogate and often speaks at his rallies, says she’s setting her sights on winning Iowa as she predicted a ramp-up.

Another Trump senior official told FoxNews.com that “the lion’s about to be unleashed” in Iowa and that he is confident Trump can take the state in the general election.

While a ramp-up in funds and paid positions has been promised, Trump’s ground game to date has been described as understaffed compared with Clinton’s well-oiled machine.

One of the oldest PACs supporting Trump – Great America PAC – isn’t likely to meet its $20 million goal by the start of the Republican National Convention. PAC official Eric Beach told Bloomberg News as of May 31, it had only raised $2.5 million. In June, it raised another $2.5 million and another $1.6 million in the first two weeks of July. The group will use the money to invest in voter-turnout efforts and pro-Trump television advertisements.