In presidential politics, we're a narrowly divided nation. The razor-thin results of 2000 showed it; President Bush's still-narrow margin in winning a second term four years ago confirmed it. And the closeness of this year's contest is demonstrated by steadily tightening polls this summer, with John McCain paring away Barack Obama's lead.

Election 2008 could go either way -- to McCain and the Republicans, who open their convention tomorrow in Minnesota, or to Obama and the Democrats, who on Thursday wrapped up their gathering in Colorado. How should voters set about deciding?

The candidates' personal histories and personalities matter, for sure. The toughest calls a president must make are dictated by unpredictable events.

Here both McCain and Obama have much to recommend them -- as, in their kinder, gentler moments, they mutually acknowledge. McCain endured great hardship in the nation's military service and has long experience in the Senate, sometimes breaking with his party's stances. Obama has forged a political ascent from modest beginnings, rising through brainpower, steadiness and ability to inspire.

Both men are American success stories. One is on the older end of the scale for presidents -- McCain would be 72 on Inauguration Day -- and the other at the younger -- Obama would be 47. But presidents young and old have done well.

Policies and key issues can help voters choose, and surely the economy is a key one. Even McCain says we're worse off than four years ago. He would retain Bush's tax cuts, which otherwise would expire in 2010, and is a staunch free-trader. Obama is more skeptical of free-trade pacts. He would end tax breaks for companies that shift jobs overseas. Also, he says he'd change tax policies to boost income for all but the highest-earners, who would see their taxes increase.

What about the increasing federal deficit? McCain has a record of opposing bloated federal budgets. Obama says he too would ferret out waste, and notes that the last Democratic president left a hefty surplus. The spending plans of both candidates, however, raise caution flags. Their rhetoric must mesh with fiscal reality.

They have sharp differences on health care. McCain favors a free-market solution based on private insurance. Obama seeks near-universal coverage through a mix of state and federal programs and private insurance. With so many interests opposed to either course, the ability to craft compromises will be key.

McCain is pro-life, opposing abortion rights. Obama favors such rights. With several Supreme Court appointments likely, the constitutionally recognized right to abortion could be at stake.

In foreign policy, the starkest single contrast is over the Iraq War. McCain sees that war -- and a victorious outcome -- as essential. Obama, a longtime Iraq War critic, stresses the need to end it. Lately, increased stability in Iraq has made a timetable for troop withdrawals, which Obama backs, less controversial.

That list of issues is hardly exhaustive. It doesn't include energy, entitlements or education. But it should be plenty, together with the two strong candidates and their running mates, to warrant Americans' close attention in the nine weeks leading up to Election Day.

Get $150+ in coupons in every Sunday N&O. Click here for convenient home delivery.