The people involved in the Trump campaign should have notified the FBI when they believed they had been contacted by a foreign government. Lesson learned.

We know that foreign governments, some of them hostile, try to build relationships with political candidates and staffers on campaigns. They do this to hedge their position if the candidate wins the election and those campaign staffers become the staff of the newly-elected politician.

Candidates and their staff should report all their interactions with foreigners to the FBI. They must also catalog all of their previous involvement with foreigners, including travel and members of their family who have foreign connections.

We have learned that the FBI was concerned enough about Russian interaction with the Trump campaign to open a counterintelligence investigation during the 2016 campaign. Is this the first campaign the FBI has investigated? The background checks on all political candidates, if there are any, should be released by the FBI for the public to review.

Bernie Sanders visited various nations who were hostile to the United States when he was an adult. He visited the Soviet Union and Nicaragua during the Cold War. His campaign benefitted from the Russian intelligence operation that stole the emails of Hillary Clinton. Without the intervention of Russian military intelligence, the Bernie Sanders campaign wouldn't have known the DNC and Hillary Clinton had rigged the election.

Greg Craig, who worked for Sen. Ted Kennedy, President Clinton, and President Obama, was just indicted in the probe that uncovered Paul Manafort's lobbying for Putin's puppet government in Ukraine.

What other candidates and their handpicked staff have connections with hostile foreign governments? What candidate has connections to think tanks that have relationships with foreign regimes?

We must purge our politics of foreign influence. The Mueller investigation was just the start of an overdue cleaning.

Chris McCarthy is the host of The Chris McCarthy Show on 1420 WBSM New Bedford. He can be heard weekdays from 10 a.m. to noon. Contact him at chris.mccarthy@townsquaremedia.com and follow him on Twitter @Chris_topher_Mc. The opinions expressed in this commentary are solely those of the author.