Two recent polls of Iowa residents show former North Carolina Sen. John Edwards continues to hold an edge in the leadoff nominating state, the Des Moines Register reports.

John Edwards has maintained his slender advantage even amid news that his wife, Elizabeth Edwards, has experienced the return of her cancer.

Also, one-time presidential candidate and former Iowa Gov. Tom Vilsack officially endorsed the frontrunner, Sen. Hillary Clinton, Monday.

The results of a University of Iowa poll, conducted March 19-25, surveying 206 likely Democratic caucus-goers, with margin of error of +/- 6 percent:

• John Edwards: 33 percent
• Hillary Rodham Clinton: 31 percent
• Barack Obama: 19 percent
• Undecided: 11 percent

All others are in low single digits.

A Zogby poll, taken Monday, surveying 506 likely Democratic caucus-goers, with margin of error of 4.5 percentage points, arrived at the following:

• John Edwards: 27 percent
• Hillary Rodham Clinton: 25 percent
• Barack Obama: 23 percent
• Undecided: 15 percent

All others are in low single digits.

For Edwards, who finished second to John Kerry in Iowa in 2004 and pretty much has to win the state in 2008, the results are very encouraging, especially given last weekend’s developments.

With a win in Iowa, he could build on that early momentum and do well with his strong union support in Nevada, which might generate hope in New Hampshire. He would then surely do well in his native South Carolina, and possibly many other states in the looming February 5 mega-primary.

It would be a potentially fatal blow if he failed to win Iowa, however. The series of events he needs to set in motion to have a chance in the 2008 election depends entirely on this victory.

As for Barack Obama, a third-place finish in Iowa historically nets enough interest and support to carry on. But his trend line isn’t moving in the positive direction. He’s drawing crowds, but so far, not their support.

Hillary Clinton, meanwhile, leads nationally and is in a virtual dead heat here. With a win, she might be able to quickly roll up the nomination the way John Kerry did after his victory in 2004. Stay tuned.