Washington DC is not usually the scene of campaign trail stops
It is a strange quirk of US politics that Washington DC, the city where so much of the national decision-making takes place, so rarely plays a role in national politics.
Because it is a federal district - separate from any of the states - it may be where Congress is located, but it does not have any full members of Congress of its own.
The city's appearance on the campaign trail tends to be as a cipher.
"Washington" becomes the symbol of a corrupt, atrophied establishment - against which the candidates like to define themselves as agents of change, no matter how long they have worked in the city or how much they lust after residence in it for the next four, or hopefully, eight years.
Mitt Romney - late of the Republican nomination race - defined himself as being "not Washington". Now, he definitely won't be for the next four years.
But, in this most compelling of presidential races, the District of Columbia finds itself with an unusual degree of relevance - as part of the so-called Potomac Primary, Tuesday's trio of nominating contests that includes neighbouring Virginia and Maryland.
Stem the tide
Timing is everything. And the voting in the states closest to the White House is taking place at what could be a pivotal point in the race for the Democratic Party's nomination.
Hillary Clinton 17 states, 1,592 delegates
Arizona, Arkansas, California, Florida, Massachusetts, Michigan, Nevada, New Hampshire, New Jersey, New Mexico, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, Tennessee, Texas
Barack Obama 24 states, 1,723 delegates
Alabama, Alaska, Colorado, Connecticut, Delaware, Georgia, Hawaii, Idaho, Illinois, Iowa, Kansas, Louisiana, Maine, Maryland, Minnesota, Missouri, Nebraska, North Dakota, South Carolina, Utah, Vermont, Virginia, Washington state, Wisconsin
2,025 delegates needed for nomination. Source AP (includes all kinds of delegates) Q&A: US election delegates
Arizona, California, Connecticut, Delaware, Florida, Illinois, Maryland, Missouri, New Hampshire, New Jersey, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, Texas, Vermont, Virginia, Washington state, Wisconsin
Mitt Romney 11 states, 251 delegates
Alaska, Colorado, Maine, Massachusetts, Michigan, Minnesota, Montana, Nevada, North Dakota, Wyoming, Utah
1,191 delegates needed for nomination. Source: AP (includes all kinds of delegates)
Barack Obama has the wind in his sails after a highly successful weekend, which saw a string of resounding primary and caucus victories.
For Hillary Clinton, it is a time of introspection and transition.
Her decision to reshuffle her campaign team - replacing campaign manager Patti Solis Doyle with another long-term confidante, Maggie Williams - is a clear sign of concern about her ability to stem the tide of Obama enthusiasm.
So can she?
Certainly, Mr Obama appears well-positioned for the upcoming contests.
Although he has shown he can attract voters across racial lines, African-Americans have been his most reliable source of support.
Washington DC is 60% African-American, while Maryland has a history of electing black officials. And Virginia, for all its history of segregation, is the state which - in 1989 - elected the country's first ever African-American governor, Douglas Wilder.
These days he is the elected mayor of the state capital, Richmond - and a committed Obama-backer.
The Clinton campaign has been playing down expectations, trying to transform the long-time front-runner into the underdog, and casting ahead to next month's votes in the delegate-rich states of Ohio and Texas.
Tuesday: Maryland, Virginia and Washington DC (multi-party)
It has also been positioning the former First Lady as the best-placed candidate to defeat the likely Republican nominee, John McCain, in a general election - although opinion polls are currently suggesting otherwise.
It may be a sensible argument, but it has some uncomfortable parallels with the strategy employed by that other one-time presidential front-runner from New York, Rudy Giuliani.
Wasn't he going to show his ability to compete across the country, after ignoring the first few primaries and winning in Florida?
And there are questions, too, on the Republican side, for the man who's been endorsed by Mr Giuliani: John McCain.
A year ago - in a bid to shore up the evangelical vote - the Arizona senator made a pilgrimage to Jerry Falwell's Liberty University in southern Virginia, shortly before the influential televangelist died.
John McCain may have to work hard to energise conservative voters
He had once referred to Mr Falwell as an "agent of intolerance"; one of several reasons why he has long been viewed with suspicion by the evangelical base.
This weekend, it was Mr McCain's distant but still-fighting rival, Mike Huckabee, who was on the campaign trail at Liberty University.
The former Arkansas governor and ordained Baptist preacher has been the candidate of choice for the religious right in this election cycle.
And while Mr McCain's nomination is a near certainty, Mr Huckabee's victories in Louisiana and Kansas at the weekend were a sign that the likely Republican candidate may need to make a few more pilgrimages if he is to energise the conservatives, whose support he will need in November.
The truth is that tepid support or indifference for Senator McCain is support for Senator Clinton or Senator Obama
John Hensarling, Texas congressman
Mr McCain has, though, picked up the endorsement of a well-known evangelical leader, Gary Bauer, who himself ran for president in 2000.
Mr Bauer pointed to Mr McCain's opposition to abortion as a reason why social conservatives should vote for him.
Another conservative who has recently endorsed Mr McCain, Texas congressman John Hensarling, adopted what could be a more persuasive argument.
"I do not wish to gloss over our differences, as they are very real," he said.
"But the truth is that tepid support or indifference for Senator McCain is support for Senator Clinton or Senator Obama."