Unity is one of the big themes of the current election.

People get unified in two different ways. Unity comes either from a common threat from the outside, or from leadership emerging from the inside.

Who can forget the shock and the surge of patriotism that followed the 9/11 attacks? The political and social divisions that define calmer times disappeared and we all became Americans.

We were united behind our president, whose approval ratings went beyond 90 percent.

Over the few short years since that shock, circumstances have changed. President Bush, once wildly popular, is now wildly unpopular.

Last month, polling showed that concerns about the economy moved past concerns about terrorism as the nation's top issue.

If we look at the two parties, the Democrats appear far more unified than Republicans.

But this Democratic unity is driven primarily by the outside-in variety. Democrats are deeply unhappy with the status quo in the country, Republicans far less so.

Only about 25 percent of Americans express satisfaction today with the direction of the country.

But the gap between Republicans and Democrats is huge. Only about 15 percent of Democrats are satisfied with how things are going, but almost 50 percent of Republicans are satisfied.

Democratic Party unity is being driven from the outside, a common dissatisfaction with the status quo, with the party uniformly defined by liberalism.

The Democratic nomination contest is about personalities, not issues. Regardless of which candidate gets nominated, Sen. Barack Obama or Sen. Hillary Rodham Clinton, 85 percent of Democrats say they will be satisfied.

It's probably the reason why Obama will be the Democratic nominee. Despite Clinton's efforts to distinguish herself from him on issues, the truth is that there is very little difference. It's a contest that will be won on personality, and he is beating her hands down in this department.

Republicans, on the other hand, are driven by an entirely different reality. Republicans are far less put off by the status quo in the country and party unity must come from the inside out. Whereas outside-in unity is driven by a commonly perceived external threat, inside-out unity must be driven by internal leadership.

As a result, the GOP contest has been far more one of issues than of personalities.

The problem is, no one Republican candidate has been able to appeal with equal strength to the major party concerns of national security, traditional values and free-market economics.

Given that 86 percent of Republicans say that "defending the U.S. against terrorism" is their No. 1 concern, perhaps it is not surprising that Sen. John McCain has emerged as the front-runner.

But, although national security is the top concern of Republicans and remains at the top of concerns for all Americans, social and economic concerns are also strong.

The unavoidable conclusion is that, if one assumes that McCain prevails as the party nominee, his choice for vice president will be crucial both for unifying the party and for the general election. He's got to pick a running mate who will bring strong credentials that satisfy the social and economic concerns of Republican conservatism.

What will this mean for the general election?

There's a sense that this is going to be a year when a Democrat will be returned to the White House.

An election year in which general public dissatisfaction is high does not bode well for the party in power. Plus, Democratic fund-raising and voter turnout is far outstripping Republican efforts.

The decisive battleground for the general election will be the third of the electorate in the middle -- independent voters and those without strong party affiliations.

These voters have migrated to the Democratic side over the past couple years. But polling indicates that this migration has been more defined by disillusionment with Republicans than with a surge of new enthusiasm for the Democratic Party and liberals.

This is supported by the fact that despite the Democratic blowout in the 2006 congressional elections, the approval ratings for the Democratic Congress are abysmal.

It is most reasonable to conclude that the Republican tent that housed party loyalists and independents for so many years is still the tent where most Americans want to be. They just need to feel comfortable that it's a tent that will be standing dependably once they are inside.

A Republican ticket that is balanced and strongly representative of concerns for national security, traditional values and a free economy can still be the winning formula.