Barney Frank has a one-line zinger to sum up Donald Trump's candidacy

Real-estate magnate and Republican presidential candidate Donald Trump has said some pretty controversial things since he announced he was running for president last month.

His comments on everything from Mexican immigrants to veterans and Sen. John McCain (R-Arizona) have landed him in hot water with members of his own party.

Democrats, on the other hand, have been relishing how Trump has grabbed attention - and leads in a number of polls.

One former Democratic congressman has neatly summed up the real-estate mogul's effect on the 2016 race - and the Democratic sentiment about his run.

Speaking with Business Insider on Monday, former Rep. Barney Frank (D-Mass.) said, "I never thought that we Democrats would be as lucky as we are to have him running for president as a Republican."

Business Insider spoke with Frank on the eve of the fifth anniversary of the landmark financial-reform law, the Dodd-Frank Wall Street Reform and Consumer Protection Act, being signed into law.

Most Republican candidates have condemned Trump's statement last weekend about McCain, who was captured and tortured during the Vietnam War. Trump said during an event in Iowa that the senator was "not a war hero." He promptly reversed himself, saying he was a "war hero because he was captured."

But so far Trump has managed to remain at or near the top of polls, which could be damaging for the Republican Party. Republican leaders have already urged him to tone down his rhetoric. And the conservative-leaning Wall Street Journal editorial board is so fed up with him they wrote a scathing takedown of the candidate on Monday.