By Yael T. Abouhalkah, Kansas City Star Editorial Page columnist

In just three days, Barack Obama has opened up a big lead over John McCain among likely voters in the Nov. 4 presidential election. The margin was 51-44 percent in Tuesday's Gallup Poll, up from 49-47 percent on Saturday.

Up until now, McCain's supporters had been holding out hope that their candidate would continue to fare well with likely voters.

Generally, these are the older people who always go to the polls and vote, a turnout that might help McCain.

And these likely voters include proportionately more middle- to upper-income voters, again a statistic that could favor McCain.

But that's not happening right now.

The news is even worse for McCain in Gallup's widely watched poll that measures how all voters (not just likely ones) feel about the upcoming election.

That traditional poll of all voters has showed showing Obama with a lead usually about 10 percentage points for most of October.

Indeed, on Tuesday, Obama's margin over McCain in the traditional poll was 52-41 percent, the same as Monday.