I’ve dealt with every presidential election since 1988 as a journalist, and I’ve been playing with various electoral vote scenario tools as Election Day approaches this time. This fact is striking me right now: I’m having a difficult time drawing up a scenario that leads to a John McCain victory.

This is my best-case scenario for McCain. It gives him 274 electoral votes — just barely over the 272 needed to become president — but it basically requires him to run the table of five key contested states: Missouri, Colorado, Virginia, Florida and Ohio. He’s currently behind in polling in all five, and I see little evidence to suggest Virginia or Colorado are within his grasp.

Here’s my best-guess outcome. It’s 291-247 Obama. Ohio and Nevada are really tough for me to call but I’m tossing Ohio to McCain (the GOP has shown again and again it can win close presidential elections there) and giving Nevada (one of the states most affected by the housing crash) to Obama. Also interesting in this scenario: McCain still takes Missouri, which has chosen the winner in every presidential election since 1904 with one exception — 1956. I’m picking McCain there because of the state’s aging population (older people are more likely to vote, and they’re also more likely to go for McCain, and that might be enough to make a difference).

And here’s my best-case scenario for Obama. This would be an electoral vote landslide. It also requires North Carolina and Florida to fall to Obama — two developments I have a hard time buying, polls be damned.

Two weeks go to. National polls seem to be leaning to Obama by 5-8 points or so. It’s worth remembering — again — that a presidential election is really a series of state elections, with the winner taking all of the electoral vote spoils in almost every state. There’s still time for anything to happen.