Party insiders speculate most of the state's Democratic congressional delegation—including Reps. Donna Edwards, Chris Van Hollen, John Sarbanes, and Elijah Cummings—as well as Baltimore Mayor Stephanie Rawlings-Blake, and U.S. Labor Secretary Thomas Perez—are all likely to look closely at the race. Rep. John Delaney tweeted his interest in a bid Monday, while sources close to Anthony Brown, last year's gubernatorial nominee, say he also is"seriously" considering it.
The one candidate who could clear the field, or at least come close, is former Gov. Martin O'Malley. But the former Baltimore mayor, who is exploring a presidential campaign, is seen as an unlikely candidate for legislative office.
Democrats say anyone from the early list of would-be senators would make for a strong contender. But complicating their decisions, strategists say, is that they would also make viable challengers in 2018 to newly elected Republican Gov. Larry Hogan, who Democrats think will be vulnerable during an election year less hostile to the party.
Like in California, where talented candidates such as Lt. Gov. Gavin Newsom passed on an open-seat Senate race while eyeing a run for governor in 2018, candidates might decide to delay their move for higher office. It adds another dollop of uncertainty to an already fluid process, especially because four months ago, Democrats didn't think either race would be in play.
"Everyone thought Anthony Brown was going to win three months ago, and they certainly thought Barbara Mikulski was going to run for Senate, so the idea that there's a camp of people that are going to wait to run for governor and a camp of people who want to be in the Senate—that just doesn't exist here because all of what's happened in the last four months is so destabilizing," said one Democratic strategist, who requested anonymity to judge the race candidly. "It's not as if there's a really long process where people had to stake their claim in one race or the other."
Democrats say it's difficult, if not impossible, to handicap the field. Interest will be high in finding a woman to replace Mikulski, the longest serving woman in Congress history, and the primary's large black electorate could push for a minority to hold the post.
But ideologically, Democrats say they see few major differences among the list of candidates, particularly within the congressional delegation.
"All of our delegation makes very valuable contributions in different areas. If you were looking at a short list, you'd expect all seven of them to be great senators," said Maryland State and DC AFL-CIO President Fred Mason. "We work well with our whole delegation, seven members."
The size and shape of the eventual field could ultimately determine who wins. A half dozen serious candidates—a scenario at least one Democratic strategist considered possible if not likely—could mean that the eventual winner would need just barely more than 20 percent of the vote. With few political differences between candidates, geography may end up playing an outsized role in paring down the field. Baltimore has traditionally claimed a stronghold over statewide Democrats, but several of the top candidates in this race tout Montgomery County ties. Multiple candidates from any one area could cancel each other out.