Updated 7:55 p.m. | Rep. Chris Van Hollen’s decision to run for Senate in Maryland marks the likely start of a crowded Democratic primary for Senate — and for his newly open House seat too.

Van Hollen represents Maryland’s 8th District, a reliably Democratic district bordering Washington, D.C. With its affluent population and proximity to the Capitol, Democrats will have no shortage of candidates who could run. Van Hollen has held the seat since 2002, and for many ambitious Democrats, this is their shot.

What’s more, members of the State Senate, House of Delegates and Montgomery City Council have little to risk by running because they are not standing for re-election until 2018.

“Maryland’s going to be an absolute circus, and especially in this seat, it could be a free for all, with some really strong candidates considering a run,” said Doug Thornell, managing director at SKDKnickerbocker and former Van Hollen aide.

“I’m not sure who wouldn’t give it some thought just because it’s a rare opportunity,” said Montgomery City Councilmember Nancy Floreen, a potential candidate for the seat. “These seats do not become open very frequently.”

Already one candidate has announced she will run: Kathleen Matthews, the executive vice president and chief global communications and public affairs officer for Marriott, Politico reported Thursday. She is a former local news anchor, and she is married to MSNBC television host Chris Matthews.

But according to several Maryland sources, she will have company. There is a long list of other candidates who could run for the seat:

• State Sen. Jamie Raskin — Popular with progressives, Raskin represents part of the 8th District in the state Senate. Raskin confirmed he is “actively exploring this” in a Thursday phone call. He said he was speaking with his colleagues, his family, and his constituents. “If people think that this is the right move then I’m feeling it and I think I’ll go for it,” he said.
• Montgomery County Councilman Hans Riemer — Riemer holds an at-large seat on the Montgomery County Council, so he represents all of the county voters in the 8th District. “I’m looking at that, for sure,” Riemer told CQ Roll Call in a Thursday phone call.
• State Sen. Rich Madaleno — Madaleno has served in the state Senate since 2007. Madaleno told the Washington Blade Thursday he is “seriously considering” a run.
• Former Del. Heather Mizeur — Mizeur ran an impressive campaign for governor in 2014 before losing in the primary. Now she is publicly mulling a bid for retiring Sen. Barbara A. Mikulski’s seat, but sources said Mizeur could run for Van Hollen’s seat instead. “She’s taking some time and weighing all her options for 2016,” said Joanna Belanger, her former campaign manager who is now helping her with press inquiries.
• Del. Bill Frick — Frick has served as a state delegate since 2007, since he won the appointment to the seat.
• Floreen — Another at-large member of the council, Floreen represents many of the voters in Van Hollen’s district. “I haven’t ruled it out at this moment in time,” she told CQ Roll Call in a Thursday call.
• Montgomery County Councilwoman Nancy Navarro — Navarro represents the part of Montgomery County that stretches from Wheaton to Etchison. Look for her to make a decision soon: She told CQ Roll Call Thursday she is “seriously taking a look” at a bid and a decision would come “in a week’s time or so.”
• Former Montgomery County Councilwoman Valerie Ervin — Ervin was the first African American woman to serve on the Montgomery County Council. She resigned in 2013 to lead the Center for Working Families.
• Del. Jeff Waldstreicher — Waldstreicher represents the only state legislative district wholly within the 8th District. In a Thursday phone call, he declined to discuss if he had any interest in the seat. “For any congressional race it’s critical that we talk about economic justice, income inequality and the strength of our labor movement,” he said.
• State Sen. Roger Manno — Manno was elected to the state Senate in 2010, after four years in the House of Delegates.
• Del. Kumar Barve — Barve, a longtime member of the House of Delegates, was first elected in 1990. “A large number of community leaders have asked me to enter this race,” he wrote in a Thursday email to CQ Roll Call. “I expect to make a decision in a couple days.
• Del. Ariana Kelly — Kelly has served in the House of Delegates since 2011. “I’m definitely thinking about it,” Kelly told CQ Roll Call in a Thursday phone call. “I have not made a decision yet.” She said she would try “to make a decision quickly.”

Manno, Ervin, Frick and Madaleno did not respond to CQ Roll Call’s efforts to contact them.

At least two other potential candidates have decided not to run: Frederick County Executive Jan Gardner and Montgomery County Councilman Roger Berliner.

“I find the House of Representatives at this moment in time not to be an appealing venue to advance the public interest,” Berliner said via phone. “And I am on the Montgomery County Council where we are able to do good things for our people. So when I consider where I can be most effective at advancing the public interest, I have concluded that local government is where I can achieve that.”

Gardner professed herself “honored” to be mentioned but wrote, “I do not intend to run,” in a Thursday email.

With so many people eyeing the seat, congressional hopefuls will need to move fast to shore up support.

“Whoever’s gonna get in, were I advising them, I’d say move quickly,” said Democratic fundraiser Michael Fraioli.

The complication? Some candidates might have another option: Rep. John Delaney, D-Md., who represents part of Montgomery County in the adjacent 6th District, is also considering a Senate bid. Several of these candidates could run in the 6th District instead and possibly avoid a crowded primary.

The 6th District race might draw a smaller Democratic field, but it’s also the most competitive in the state. Delaney defated the Republican nominee, Dan Bongino, by 1.2 points in 2014, a terrible year for Democrats in Maryland. President Barack Obama won the district with a 55 percent in 2012, compared to the 61 percent or more with which he won every other Democratic-held seat in the state.

In almost any cycle, Democrat are favored to hold Van Hollen’s seat. Obama won the seat with 62 percent of the vote in 2012, and Van Hollen won re-election with 60 percent of the vote in 2014. The outcome of this race will not affect Democrats’ overall calculus in the House, where they need a net gain of 30 seats to take the majority.

With five of the other Maryland House Democrats openly considering Senate bids, in addition to Van Hollen, Maryland Democrats could see a huge upheaval in their ranks, with primaries for any number of House seats.

But a lot of uncertainty remains. Maryland’s filing deadline is not until January 2016. A House member who says they are running for Senate now could be running for re-election by January.

“You can always say yes now and no later,” Rep. Steve Israel of New York, the former Democratic Congressional Campaign Committee Chairman said Wednesday shortly before Van Hollen announced his Senate bid. “So there’s a lot of time and space where people have to decide whether or not they’re going to run for their own seats.”

Correction, 6:55 p.m.

A previous version of this story misidentified the location of Madaleno’s district.

Correction, 7:35 p.m.

A previous version of this story misidentified Delaney’s district.

Related:

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The Maryland Democrat Who Wants to Stay Where He Is

Is the Senate Where It’s At for Ambitious House Democrats?

Long List of Possible Barbara Mikulski Successors

Mikulski Will Not Seek Another Term (Updated)

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