If the Democrats have the Super Tuesday many, myself inclded, expect them to have, DNC chair Howard Dean will likely release the loudest scream he's ever produced--and rightfully so. With his Democracy for America grassroots party building initiatives(and Barack Obama's candidacy has certainly helped that)--the Democrats are poised to have a majority in two or perhaps all three branches of the federal government, as well as many gains on the state level.
The crucial step for the Democrats will be to prove that they have earned the trust of those who voted them. This will be a far more difficult thing to accomplish. Whether it is fair or not to say, the last eight years have actually set the bar far higher for the next administration because of the waste of all kinds of capital--human, social, and political.
The issue for the Democrats will be to show discipline and focus in delivering on the campaign promises made. For all of our sakes, we had better hope and be prepared to hold their feet to the fire so that they are not blinded by power (as so often is the case when one party holds sway). The checks-and-balances here are that the Republicans, independents, and the party's own grassroots can be very unforgiving.