The poll -- conducted by Opinion Research for CNN and released Friday -- found that only 54 percent of those surveyed said they would not vote for Obama for president. Among registered Democrats, 43 percent said that they would prefer Clinton to be the party's nominee.

In a similar survey in early June, 35 percent of Democrats backed Clinton and 60 percent of Clinton supporters planned to vote for Obama. The number of Democrats backing Obama has also dipped from 59 percent to 54 percent.

The latest poll was done after Clinton and Obama got together in Unity, N.H., for a display of party unity.

CNN polling director Keating Holland said the big question is whether Clinton's supporters will come around and support Obama, instead of staying home on Election Day, or even voting for presumptive Republican nominee John McCain.

"Many voters find it tough to immediately switch allegiances to a candidate that they once opposed, so they find a 'neutral' setting more comfortable for awhile," said Holland.