The Des Moines Register features its latest Iowa poll in the Sunday edition, showing Barack Obama leading John McCain 52 percent to 40 percent among likely voters. The poll surveyed 801 Iowans by telephone, including 616 who said they would definitely vote in November.

If you click the link you can read the exact wording of questions asked, but it’s not clear whether the likely voter screen involved anything other than whether a person said he or she would definitely vote.

It’s the second poll in a row to show Obama above 50 percent in Iowa, with a double-digit lead. A Time/CNN poll taken after McCain selected Sarah Palin but before Palin and McCain spoke at the Republican convention showed Obama beating McCain 55-40 in Iowa, leading in every region of the state and even among rural voters.

Other findings from the Des Moines Register’s new Iowa poll:

Just 18 percent of respondents think the country is headed in the right direction, while 74 percent say it is on the wrong track.

George Bush is at 25 percent approval, 71 percent disapproval. Repeat after me: most unpopular president in history!

Tom Harkin leads Christopher Reed in the U.S. Senate race by 53 percent to 34 percent.

Chuck Grassley’s approval rating is still high at 69 percent. Democrats’ only hope is to pick up so many Senate seats this year that Grassley decides to throw in the towel before the 2010 election. He hasn’t been getting along too well with Iowa Republicans lately, and it’s never fun serving in the minority in Congress.

I love that McCain and Sarah Palin will waste part of this Thursday campaigning at the Eastern Iowa Airport outside Cedar Rapids. Sorry, but Iowa is not really a swing state in this year’s presidential race.