John McCain now needs only about 300 delegates to win the GOP nomination outright. Barack Obama has surged into the lead in the Democrat delegate count. And all this with just three primaries on a single day.

Senator Barack Obama rolled to victory by large margins in Virginia, Maryland and the District of Columbia on Tuesday, extending his winning streak over Senator Hillary Rodham Clinton to eight Democratic nominating contests.

The outcome provided him his first chance to assert that the Democratic race, which had seemed to be heading into a protracted standoff, is beginning to break in his direction. And it left Mrs. Clinton facing weeks in which she has few opportunities for the kind of victory that would alter the race in her favor after a string of defeats notable not just for their number but also their magnitude.

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In Tuesday’s contests, Mr. Obama showed impressive strength among not only the groups that have backed him in earlier contests — blacks, younger voters, the affluent and self-described independents — but also among older voters, women and lower-income people, the core of Mrs. Clinton’s support up to now, according to exit polls. Mr. Obama also won majorities of white men and Hispanic voters in Virginia, though not in Maryland.

With almost all precincts reporting, Mr. Obama won 75 percent of the vote in the District of Columbia and 64 percent in Virginia. He had 60 percent of the vote in Maryland with results from 67 percent of the precincts.

On the Republican side, Senator John McCain won in Virginia over Mike Huckabee, the former governor of Arkansas, virtually eliminating any threat that Mr. Huckabee might have posed to Mr. McCain’s status as his party’s all but certain nominee.

Mr. Huckabee got a boost from conservative and evangelical Christian voters in the state, but not enough to overcome support among moderates and nonevangelical Christians for Mr. McCain, who won 50 percent of the vote. Mr. McCain also prevailed in the District of Columbia, with 68 percent of the vote, and in Maryland, where he had 55 percent of the vote with 67 percent of the precincts reporting.

My fellow Republicans, it is time to accept the reality that this race is over on our side. Barring a miracle -- like winning every remaining state with 75% of the vote -- Mike Huckabee is effectively out of the race for the nomination EXCEPT as a way of expressing your discontent with McCain, something I feel is better done by casting your vote for the candidate of your choice (in my case Mitt Romney) than for the last challenger standing. But regardless of this race, remember it is still important for you to vote in the primary because of all the down-ballot races, whether we are talking about Congress, the state legislature, or local races.

On the Democrat side, I see a stark choice. The Democrats have to decide between a moderately qualified candidate with high negatives and an ill-defined novice whose appeal is more charismatic than anything else. A vote either way sows dissension, due to the skill with which each side has played interest group politics and divided the voting blocs within their party. Ultimately, I urge Democrats to remember that the important thing is not which first comes first, but rather which candidate will be a more effective president. I don't pretend to offer advice as to which one that is, simply ask that you pick wisely for the good of the nation.