Elizabeth Warren, the Democrat who is running for Scott Brown's U.S. Senate seat in Massachusetts, is nearly keeping pace with Mitt Romney's astronomical fundraising levels, according to the latest figures released Monday by each campaign.

If the measurement is money raised per voter, rather than total dollars, that is. In the month of June, according to calculations performed by Yahoo News, Romney raised 77 cents per registered voter in the United States. Warren is right behind him, pulling down 75 cents for every registered voter in Massachusetts.

Here's the math: Romney's campaign and a joint committee the candidate formed with the Republican National Committee together reported raising $106 million in June. Using census data for the 2010 election, there are more than 137 million registered voters in the United States. Divide those numbers together and you get the per-voter number: 77 cents.

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In Massachusetts, Warren raised $3.1 million in June. There are more than 4.1 million voters in Massachusetts, according to state totals released earlier this year. (The same census tables used for the 137 million national figure estimated about 3 million registered voters in Massachusetts, but Yahoo News' mathematicians decided to use the more recent state figure at the expense of an apples-to-apples comparison.) Dividing $3.1 million by the 4,111,128 voters in Massachusetts gets you Warren's dollars-per-voter number: 75 cents.

Working in Romney's favor at the dollar-per-voter level is that Warren's campaign total was for her campaign coffers alone while Romney's total included money raised by both his campaign and the joint committee he set up with the Republican National Committee. The Romney campaign did not divulge how much money was raised by his campaign alone.

Romney raised an average of $3.5 million a day in June. Warren's campaign said June was the candidate's "most successful single month since the start of the campaign."

Chris Wilson contributed to this story.