DENVER  The reality in Colorado is that a big piece of the election is already over.

The state’s heavy emphasis on mail-in and early voting means that close to 1.5 million votes, or about 46 percent of the registered total, are already in the can, cast and waiting to be counted.

That means two things. First, that a surge, or a misstep, at the last minute can only help or hurt so much, since voter decisions were in many cases made on conclusions reached in mid-to-late October. Second, it mandates, in a still-tight race, a pinpoint, surgical search for the votes still left.

Mary Ann Larsen and Diane Tapia-Gonzales, who knocked on doors in the Denver suburb of Arvada on Thursday night as volunteers for Senator Barack Obama, the Democratic nominee for president, epitomized the new narrow-cast focus. On their computer-generated lists, every name came with a one-to-five scale based on prior contact  one being committed to Mr. Obama, five being four-square for the Republican nominee, Senator John McCain. The women knew who had already voted  updates come in daily from local county clerks  and who had a mail-in ballot in hand not yet submitted.

Mr. McCain’s campaign is similarly obsessed with the details.

“Everyone knows which votes are turned in and where the votes are that are left,” said Tom Kise, the campaign’s communications director for its south central region.