Another log has been added to the fire in the increasingly heated Democratic congressional primary playing out in the Maryland suburbs.

State Sen. Rob Garagiola and financier John Delaney — Democratic candidates for the seat currently held by Rep. Roscoe Bartlett (R) — have been squabbling for weeks about both policy and personal issues. The latest front is campaign donations, as Garagiola attacked Delaney for having contributed $2,400 to current Republican Rep. Andrew P. Harris in October 2010, just days before Harris succeeded in ousting Rep. Frank M. Kratovil Jr. from the Eastern Shore-based 1st district.

“A financial contribution to Republican Andy Harris is an act against our Democratic Party, and it’s a sign that Delaney isn’t a real Democrat. This is something Mitt Romney would do,” Garagiola said in a press release.

(Garagiola’s camp previously sought to link Delaney to Romney by accusing him of hiding his tax returns and not paying enough taxes.)

In a lengthy statement, Delaney’s campaign did not explain why he had given to Harris, instead emphasizing his longtime financial support for Democratic candidates and causes. The campaign noted that Delaney had given more than $100,000 combined to the state and national Democratic parties and raised more than $800,000 for Hillary Clinton’s 2008 presidential campaign, among other efforts.

Delaney also tried to turn the tables on Garagiola for the latter’s past career representing health-care industry clients for the lobbying firm Greenberg Traurig. “The real tragedy here is that instead of attacking a life-long Democrat who has helped dozens of Democrats get elected, Garagiola should have come clean about his own Republican ties,” Delaney’s campaign said.

It’s not uncommon for political novices, particularly those coming from the world of business, to have contributed to both parties. In Virginia, for example, Democratic congressional candidate Paul Hirschbiel has had to explain why he donated to George W. Bush’s presidential campaign in 1999 and Mitt Romney’s in 2007. And the man Hirschbiel is trying to beat, Rep. Scott Rigell (R), similarly took flack for having given to the campaigns of Democrats Barack Obama and Mark Warner.

But the donation by Delaney to Harris could be more problematic, both because it was more recent and because many Maryland Democrats strongly dislike the devoutly conservative Harris and were so sorry to see Kratovil lose. (Kratovil was appointed in December to be a Maryland District Court judge.)

Seeking to drive that point home, Garagiola’s campaign included in its release a quote from Kratovil’s wife, Kim Kratovil, who said: “Certainly people have the right to support Andy Harris, but the fact that someone running for Congress as a Democrat would max out to him the week before an election is cause for question as to whether he shares the beliefs of the Democrats or those of Andy Harris.”

All of Delaney’s past donations to Democrats show up in Federal Election Commission records as coming from “John Delaney” of “Capital Source.” But his donation to Harris — on page 52 of this report — appears under “J Delaney,” employed by “CS,” making it harder to find using a basic electronic search.