The race for U.S. Senate in Massachusetts is the most expensive congressional race in the country. And Democratic candidate Elizabeth Warren just announced her biggest monthly haul yet: $3.1 million in the month of June out of a total of $8.6 million in the last reporting quarter.

With just four months to go until the election, Warren now has $13.5 million on hand. Republican incumbent Sen. Scott Brown hasn't yet released his latest fundraising figures. But at the last reporting period, he had nearly $13 million in his campaign coffers.

That means there could be a lot of money — and ads — coming down the pipeline as we get closer to Election Day.

Guest:

More: