Long before he moved to Washington, Donald Trump stood before a crowd of midwestern voters and asked them what kind of person would want to "take a vacation" if they were living in the White House.

"What's better than the White House? Why these vacations?" he wondered aloud, taking a dig at then-President Obama's luxury getaways and weekend golf excursions.

So when Trump boarded Air Force One for his seventh trip to Mar-a-Lago since taking office, conservatives were left scratching their heads. And by his eighth trip to the sprawling beachside resort, some were speaking up.

"I do wish he would spend more time in Washington," Iowa Republican Sen. Joni Ernst told a town hall audience this week, during a visit to the first-in-the-nation caucus state where Trump had criticized his predecessor's travel habits more than a year ago.

Ernst, a member of the Senate Armed Services Committee, said the president's frequent visits to West Palm Beach are quickly becoming a security concern for herself and her colleagues. Trump has welcomed several foreign leaders to his Mar-a-Lago resort since taking office, including hosting a recent two-day summit with Chinese President Xi Jinping.

"That has been bothering not just me but some other members of our caucus," Ernst told the crowd, suggesting that Trump would be better off keeping diplomatic visits and other business "in Washington, D.C."

Security concerns surrounding Trump's visits to Mar-a-Lago accompany existing anxieties about the mounting costs of his weekend jaunts.

A roundtrip flight to West Palm Beach, Fla., on Air Force One typically costs around $700,000, the conservative watchdog Judicial Watch explained in an email to the Washington Examiner. If the first lady travels separately from New York, which has often been the case, air travel alone can cost an additional $168,000.

Politico recently estimated that the costs incurred from one weekend trip to Mar-a-Lago could be as much as $3 million once overtime pay for security personnel and costs associated with the presidential convoy and local traffic control are included. The Government Accountability Office released a report last year that found Obama's four-day trip to Palm Beach in 2013 cost taxpayers $3.6 million.

Miriam Weaver, a conservative blogger who co-founded the website "Chicks on the Right," recently urged the president's supporters to hold him accountable on the issue of presidential travel.

"I'm not suggesting he's not working hard. It's obvious that he is. That's not my issue. My issue is that he's spending way too much taxpayer money doing it," Weaver, who endorsed Trump in both the primary and general election, wrote on her blog last week.

"I'm tired of the lack of accountability on this issue," she added. "I can't be the only conservative who feels this way."

Reached by phone, a senior White House official echoed what press secretary Sean Spicer and other West Wing aides have said about the president's travel.

"Every time [Trump] goes down to Mar-a-Lago, he is working," the official said, adding that the president has been "conducting business down there for years."

"He feels comfortable there, which is conducive to negotiations," the official added.

Those who had hoped that Trump would stay put in Washington once Mar-a-Lago closes for the summer season were likely disappointed to learn this week that the president could soon make Bedminster, N.J., his new weekend White House.

"I think we're preparing, assuming it's going to happen," Bedminster Mayor Steve Parker told a local media outlet on Wednesday.

Parker has already requested the federal government's help in dealing with the security costs his township might incur if the president retreats to his northern home.

Trump conducted a number of meetings with potential Cabinet secretaries during his presidential transition at the northern New Jersey estate, which he last visited in January. Anticipating that Trump would make his way to Bedminster at some point during his presidency, Parker asked federal officials for help with security costs even before the new administration took over.

"We want to welcome President Trump with open arms, but we don't wish to burden our taxpayers disproportionately for these visits," the Republican mayor wrote in a December letter to Congress.