Maryland Democratic Congressman Chris Van Hollen has announced that he will run for the Senate seat being vacated by Barbara Mikulski, who is not seeking re-election in 2016. Open Senate seats don't come up often in Maryland: The last one was in 2006, when Paul Sarbanes retired after 30 years in the Senate; the last ones before that were in 1986, when Republican Charles Mathias retired, and 1962, when Republican John Marshall Butler retired. So the current open seat race is only the fourth in 54 years. No wonder it's tempting, and all six of Van Hollen's Maryland Democratic House colleagues have been reported as interested in running. Certainly the Democratic nominee will be favored to win in a state that voted 62 percent for Barack Obama in 2012, even if Republican Larry Hogan just won the race for governor.

But it is by no means certain that Van Hollen will be the Democratic nominee. Maryland has the fourth highest black percentage of any state, and in the 2006 Senate primary a competent black candidate, Congressman Kweisi Mfume, came close to beating a competent white candidate, Congressman (now Senator) Ben Cardin in the Democratic primary: Cardin won by a 44 percent to 41 percent margin. Currently Maryland has two competent black Democratic House members, Elijah Cummings and Donna Edwards, either of whom could be a formidable candidate, capable of winning especially if another competent white candidate, like Congressman John Sarbanes or Congressman John Delaney, runs.

Van Hollen currently has a safe House seat, which voted 62 percent for Barack Obama in 2012. He is ranking Democrat on the House Budget Committee and has been appointed to party leadership posts, chairing the House Democrats' campaign committee in the 2008 and 2010 cycles. In 2006 incoming House Speaker Nancy Pelosi created a special assistant Democratic leader post for him. He's clearly a very smart guy, with good political instincts and impressive knowledge of policy. It's no surprise that, at 56, he's widely seen as the next House Democratic leader after Nancy Pelosi, 74, Steny Hoyer, 75, and James Clyburn, 74.

So why would Van Hollen be willing to give up a safe House seat and a likely high leadership position for a risky Senate race? One reason is that there is no sign that Pelosi, Hoyer or Clyburn are interested in retiring. A second reason is that he may calculate that Democrats are not likely to regain a majority in the House, at least until the first election after the next redistricting cycle, i.e., 2022. Being in the minority party in the House is very frustrating, much more so than being in the minority in the Senate. Van Hollen has been on track to become speaker of the House some day, but that day looks to be far away.

The third thing that may be impelling Van Hollen is if he, like so many politicians, thinks he might have a chance to be president some day. That's not preposterous. If he is elected to the Senate in 2016, he will be up for re-election in 2022, which is to say that he could run for president in 2020, when he will be 61, or 2024, when he will be 65, without giving up his Senate seat. And the Democratic party, as we can see from the underwhelming array of plausible opponents to Hillary Clinton this year, is generating very few plausible presidential candidates these days. A Senator Chris Van Hollen could be one.