The field of candidates planning to run for House and Senate contests in Maryland is not yet set, but the race for campaign cash is well under way.
The potential for crowded primaries in those races has forced an intense early fundraising effort.
"They've been at it for a number of weeks," said Annapolis lobbyist Bruce Bereano, a longtime observer of Maryland politics. "People are getting phone calls and being solicited."
The average cost of a winning Senate campaign in 2012 was more than $11 million, according to the nonpartisan Center for Responsive Politics. In Maryland, the cost of television advertising in the expensive Washington media market could put the state's contest on the high end of the scale.
Mikulski's decision to retire after 28 years in the Senate has created a domino effect rarely seen in Maryland: Most of the state's House members are at least considering a run. And their interest has opened up races for the House seats they would leave behind.
Potential Republican candidates, for now, are moving more cautiously. Democrats enjoy advantages in Maryland: Registered Democrats outnumber Republicans by more than 2 to 1, have held the state's two Senate seats since 1986, and expect turnout in a presidential election year to be high.
Among Democrats, Reps. Chris Van Hollen of Montgomery County and Donna F. Edwards of Prince George's County — the only two who have declared themselves candidates — were emailing solicitations to donors in the days before the close of the first quarter on Tuesday.
"When I jumped into the race to succeed Senator Barbara Mikulski, I knew that the only way we could run this campaign is with a massive grassroots effort," Van Hollen wrote in one email. "Please consider a contribution before our important March 31st filing deadline."
On Wednesday, Van Hollen's campaign said it had raised more than $1 million since Mikulski's announcement in early March — a large sum over a short period. The candidate entered the second quarter on Wednesday with about $2.5 million in the bank, campaign aides said.
That sum, and the speed with which he raised the $1 million, could give pause to others who are considering a campaign but have never had to raise that amount of money.
The Edwards campaign, which got under way about a week after Van Hollen's, declined to comment on his numbers — or offer insight into its own fundraising.
A spokeswoman for Emily's List, a group that has endorsed Edwards, suggested Van Hollen's early haul would have little bearing on the race.
"This Senate race is about the voters, not special-interest money," spokeswoman Marcy Stech said in a statement.
Van Hollen, a former chairman of the House Democrats' campaign organization, can tap a national network of donors for support. Edwards appears likely to rely more on outside groups, such as Emily's List, to help raise money. Her campaign said Wednesday it hired a manager who previously worked for the group.
The dynamics in the House races, including for Edwards' 4th Congressional District, are different. Former Lt. Gov. Anthony G. Brown, a Democrat who is running for the seat, has a large pool of potential donors on which to draw — a product of his unsuccessful campaign for governor last year — and has been aggressively soliciting funds.
But Brown also has what is perhaps the most complicated campaign finance challenge of anyone in the state: an outstanding $500,000 loan made by the Laborers International Union in the waning days of last year's election. The debt is connected to his state account, which is separate from the fund he will use to run for federal office, but watchdog groups said they're wary of the arrangement.
"It raises a lot of concerns for us," said Jennifer Bevan-Dangel, executive director of Common Cause Maryland. "If people are giving your campaign money, it's supposed to be to further your candidacy. It's not supposed to be to get you out of trouble."
Brown lost the general election to Republican Gov. Larry Hogan.
The arrangement could allow a donor to give the maximum contribution permitted under federal law to Brown's House campaign but then cut a separate check to the state account to help pay down the debt. A campaign spokesman declined to say whether Brown would raise money in both accounts at once.
"Anthony Brown always has and always will hold himself to the highest ethical standard," spokesman Jared Smith said in a statement, "and no campaign contribution will ever change that fact."
Rep. John Sarbanes, who is considering a Senate bid as well, also has an unusual campaign finance challenge.
The son of longtime Maryland Sen. Paul S. Sarbanes can undoubtedly raise money. But for the past several years the Baltimore County Democrat has set a self-imposed limit on large donations to test a proposal he believes would shift the emphasis away from big money to small-dollar donors.
While it's one thing to test the effort in a safe House district, it's another to do it in a competitive Senate contest.
Asked recently if he would hold a potential Senate campaign to the same limits, Sarbanes focused instead on a commitment he's made to reject money from political action committees.
"I'm not here to make an irrevocable pledge," he said, "but I will say I feel like I've benefited in terms of my creativity and in terms of being able to make the case for campaign finance reform by having decided five years ago to go PAC-free."