Senator Barack Obama is gaining on Senator Hillary Clinton in the latest poll from Reuters/Zogby. John Whitesides reports for Reuters:

Clinton led Obama 38 percent to 27 percent in the new poll, a 10-point fall from her 46 percent to 25 percent lead last month. The drop followed a month of attacks on the New York senator from her rivals and a heavily criticized performance in a late-October debate.

Former Sen. John Edwards of North Carolina remained in third place, climbing four points to 13 percent. All other Democratic contenders scored in low single digits, including New Mexico Gov. Bill Richardson at 4 percent.

About 14 percent of Democratic voters nationwide are still uncertain of their choice as the first contest approaches in Iowa, which kicks off the state-by-state battle to pick candidates for the November 4, 2008, presidential election.

Read the whole story at the above link. Clinton still commands a strong lead, but this result tends to confirm (if the trend holds in other polls, too) what many have long suspected: her support is very broad among Democratic primary voters, but not at all deep. For Obama to have sliced her lead in half in only three weeks demonstrates her vaunted "aura of inevitability" is more smoke and mirrors than glowing glory.

Hillary cannot do much to change this; she has set course for a frontrunner's campaign, focusing more on her general election prospects as her competition dithered aimlessly. Now she steps up her attacks on Obama, particularly on his thin experience, but what else can she do?

Her best bet may well be to finish third in Iowa, on the theory that if either Obama or Edwards were to finish third, they would be damaged to the point of being forced out of the race (Obama could keep a healthy nest egg for 2012). That wouldn't be good for Hillary, as her support has always been shy of an absolute majority, and if either of her major challengers were to fall by the wayside, it would leave the other to become the "Not Hillary" candidate. It's in her interest to keep both Obama and Edwards in the race through the first few primaries - once she builds a lead in actual delegates won, the foreshortened schedule would leave little time for the surviving alternative to play catch-up.