John Dowd JB Reed | Bloomberg | Getty Images

President Donald Trump's personal lawyer in the Russia probe, John Dowd, contributed more money last year to the president's re-election campaign than is legally permissible, according to a recent letter from the Federal Election Commission to the Trump campaign. Dowd is Trump's lead counsel, charged with crafting the president's response to the special counsel's investigation into alleged Russian meddling in the 2016 election. A veteran white-collar defense attorney and a politically active Republican, Dowd's understanding of how Washington works has made him a key member of the president's legal team. But a March 8 letter from the FEC to Bradley Crate, the Trump campaign treasurer, put the campaign on notice that there were 108 donors who had made "excessive, prohibited and impermissible" contributions to the Trump campaign in the last quarter of 2017. Dowd's name appeared on this list, below. The X is for donations that require additional details.

Under federal law, the maximum amount an individual may contribute to a political campaign, per election, is $2,700. But Dowd has given a total of $3,000 to Trump's 2020 general election campaign, according to the tally the FEC sent the Trump campaign. Crate told CNBC that the campaign sent Dowd a refund check for $300 on January 3, a few days too late to be reflected in their fourth quarter filing to the FEC. He said it will appear on its next quarterly report to the FEC, to be released in April. Dowd said he had received the check. It's not uncommon for individual donors to accidentally contribute more to a candidate than the legal maximum of $2,700. But Dowd's case is unusual, both because of the donor and because of the date, said Brendan Fischer, senior counsel at the nonprofit, nonpartisan Campaign Legal Center. "These kinds of errors are understandable when made in the midst of a hectic election season by a rookie campaign. But they become more difficult to understand when made by a second-term presidential candidate 32 months out from his next election," Fischer told CNBC. "And it is even more difficult to understand how the president's lawyer managed to exceed contribution limits." "This is pretty embarrassing for the Trump campaign and for Dowd," said a prominent D.C. election attorney who spoke to CNBC on the condition of anonymity. As for who bears responsibility for the fact that Dowd's Oct. 1 contribution was above the legal limit, and yet was accepted by the Trump campaign, experts said both the donor and the campaign share culpability.