March has seen a fundraising blitz as candidates, members of Congress and campaign committees rush to swell their coffers before the March 31 quarterly reporting deadline.

This month was the busiest for fundraising since last September, the height of the 2010 midterm campaign, according to the Sunlight Foundation, which tracks lawmakers' fundraising. There were at least 500 events held in March, almost double the number that were held in February.

In addition to a flurry of email pitches, Democrats have been deploying their top draws to rake in the cash. President Obama was in New York City Tuesday night for two fundraising events that reportedly raised some $1.5 million for the Democratic National Committee. His appearances followed several high-profile events headlined by Vice President Joe Biden.

Republicans have been doing the same thing. New Jersey Gov. Chris Christie, for instance, is set to headline the National Republican Congressional Committee's annual dinner Wednesday, which has brought in more than $10 million. And Republican National Committee Chairman Reince Priebus said this week he's "spending 5-6 hours a day on the phone raising money."

The spring rush comes at a time when the presidential race has yet to gear up, which means there's an opening for congressional candidates and lawmakers to make their pitches to donors who aren't yet weary of opening their checkbooks.