Democratic 2020 U.S. presidential candidate and former U.S. Vice President Joe Biden walks through the Iowa State Fair in Des Moines, Iowa, August 8, 2019.

Officials in Joe Biden's presidential campaign are trying to limit his interactions with federal lobbyists while the campaign disavows contributions from donors in the influence industry.

During recent fundraisers Biden campaign officials have blocked lobbyists from private meetings with the former vice president in order to avoid a perception that his run for president is associated with the lobbying industry, according to people familiar with the efforts.

Still, that hasn't stopped Biden from meeting outside of fundraising venues for brief interactions with individual lobbyists who have known him for decades, these people added.

Biden established connections with lobbyists over his expansive career in public service, including his decades-long tenure representing Delaware in the U.S. Senate. Over 35 years, lobbyists gave Biden just over $500,000, according to the nonpartisan Center for Responsive Politics. Of that, $165,000 was given for his 2008 presidential run.

His political action committee, American Possibilities, also often received contributions from those in the lobbying industry. The PAC is scheduled to shut down in the coming months.

Biden has sworn off lobbyist contributions for the 2020 election and has yet to have a fundraiser hosted by a registered lobbyist.

Registered lobbyists want to have a role within the campaign's fundraising apparatus, as they look to advise Biden on putting more resources into states beyond early primary locations, such as New Hampshire and Iowa, according to a lobbyist who spoke on the condition of anonymity. Still, they have been unable to break through the campaign's inner circle, which has shielded the candidate from such engagement, according to Biden associates.

"They have high sensitivity on dialogue with lobbyists. They have been frozen out on the money," a person close to Biden explained.

Steve Ricchetti, one of Biden's longtime advisors, has been acting as a gatekeeper for some who want to meet with the former vice president. Behind closed doors, these people have said Ricchetti blocked their access. Ricchetti himself was once a lobbyist and advocated for pharmaceutical giants such as Novartis, Eli Lilly and Sanofi, according to disclosure forms.

In April, Biden pledged that he would not accept any campaign contributions from registered lobbyists. A few of the fundraising events have been hosted by public affairs executives with links to the government relations industry, but they are not currently registered as lobbyists, records show. Some of these hosts, however, have done past lobbying work.

A spokesman for the Biden campaign declined to comment. Ricchetti did not respond to requests for comment.

In the second quarter, Biden's campaign took in at least $6,000 from a handful of registered lobbyists that represent major corporations, including Google and Lockheed Martin. But the campaign told the Associated Press it would return those donations. The total represents only a small fraction of the $21.5 million Biden raised over that time period.

Biden continues to lead in national polls of Democratic primary voters. The Real Clear Politics polling average shows him ahead of Sens. Elizabeth Warren, D-Mass., Bernie Sanders, I-Vt., and Kamala Harris, D-Calif.

Biden's campaign efforts to avoid lobbyists come while other Democrats running for president are also attempting to shy away from having any ties to people in the industry. Most of the candidates have sworn off money from lobbyists and special interest groups out of concern that progressive organizations could argue that they're controlled by big corporations.

Last year, companies combined to spend at least $1.7 billion on lobbying activities, according to the nonpartisan Center for Responsive Politics. Some of the companies that invested in lobbying in 2018 include Alphabet Inc., Facebook, Amazon and Lockheed Martin.