David Gergen | BIO

AC360° Contributor

CNN Senior Political Analyst

With victory almost in his grasp, the looming question for Barack Obama is whether he will squeak by or whether he can roll up the score. It will matter enormously to his leadership as President.

For Obama supporters, just climbing to the top of the mountain with 270 electoral votes has always seemed daunting enough. And they are right. After all, Democrats have seen triumphs slip away from them so often - they have lost 7 of the past 10 presidential elections - that they are extremely uneasy that the Republicans can pull an upset this time, too. It seems unlikely after a raft of national polls this weekend showed Obama with a national lead of around 7 points - and by some estimates in double digits. Still, there were also unsettling state polls last night by the Mason Dixon firm showing McCain closing in fast in North Carolina, Virginia, Ohio and Missouri. Who can say for sure that Pennsylvania will remain blue. It ain't over 'till it's over.

But when the dust clears and if the Democrats have pulled it off, the Obama team will care a great deal about the size and breadth of victory. Much of his early presidency will hang in the balance.

There are three keys to watch on Tuesday night:

1. Percentage of the national vote. Right now, there is a solid prospect that Obama can rack up 51 percent or more of the total vote. If so, he would be the first Democrat since Jimmy Carter to win a majority of the national vote (Carter had 50.1 percent) and only the second Democrat since Franklin Roosevelt to claim a majority (Lyndon Johnson was the other). That historic standing would give Obama a fresh boost as the president-elect and would mean that he could run ahead of Members of Congress in their own states. In Washington, that gives a president extra power.

2. Number of red states won. In recent campaigns, Democratic presidential contenders have won mostly on the east and west coasts and the upper midwest. John Kerry only won 19 states plus the District of Columbia, and one could get on a plane at Dulles and fly to Los Angeles without flying over a state that the Democrats won.

Obama has had a vision since his convention speech in 2004 of Democrats becoming a national party, getting beyond the traditional red/blue divides. And he now has a good chance of doing it. If he can win a couple of southern states, plus two or three states from the Rocky Mountains, not to mention more Midwestern areas, he can claim a true national victory - and he would have the makings of a new, majority coalition for the Democrats, something they have lacked for decades.

3. The size of Democratic wins in the Senate and House. The Democrats were heading toward significant pick-ups with or without a presidential win, but if Obama racks up a convincing victory and is accompanied by nine or more new Democratic Senators and a couple of dozen new House members, that will give him muscle on Capitol Hill that few Presidents have enjoyed. I was working for Ronald Reagan in 1980 when he trounced Jimmy Carter and Republicans swept to 12 pick-ups in the Senate and 33 in the House. Reagan was much more respected - and effective - in working with Congress because of that thumping victory.

So, the eyes of the Obama team will be focused on getting to 270 electoral votes tomorrow night, but those who care about governing - and Obama cares more than most appreciate - will be watching, too, to see how big and broad a victory he can achieve. It could be an historic night in more ways than one.