WASHINGTON (CNN) -- A new national poll suggests the battle for the Democratic presidential nomination between Sens. Hillary Clinton and Barack Obama is a tie.

Sen. Hillary Clinton speaks Monday at a town hall meeting in Hammond, Indiana.

Forty-six percent of registered Democratic voters questioned in a CNN/Opinion Research Corp. survey released Thursday support Obama as their party's nominee and 45 percent back Clinton.

It's a statistical tie when taking into account the poll's 4.5 percentage point sampling error on that question.

"In mid-March, Obama had a 52 percent to 45 percent edge over Clinton, but his support has dropped six points while she has not gained any ground," said Keating Holland, CNN polling director.

He said "6 percent now volunteer that they want neither one to be the nominee; no Democrats in the March poll felt that way."

"Obama has lost his edge,'' said Bill Schneider, CNN senior political analyst. "Is it because of the controversy over his former pastor, Jeremiah Wright? While most Democrats have an unfavorable opinion of Wright, only 19 percent say Wright's statements have made them less favorable to Obama. More than two thirds say they've had no effect at all."

"The bigger problem appears to be Obama's string of losses to Clinton in big states like Pennsylvania and Ohio. Those losses have not driven up Clinton's support. But they may have created doubts about Obama's ability to win," Schneider said.

But the poll suggests Wright certainly doesn't help the Illinois senator. Watch more on the Democratic primary race »

"Among all Americans, Wright gets a 59 percent unfavorable rating; only 9 percent of the public has a favorable view and a third are unfamiliar with him. Among Democrats, the figures are virtually the same," Holland said.

"Roughly a quarter of registered voters and roughly one in five Democrats say they have heard about Wright's remarks and think less favorably about Obama because of them. Most, however, say their view of Obama did not change after hearing about Wright."

The poll also indicates the public is more familiar with Wright now than they were in March, when he first became a presence in the campaign, but the number who feel less favorable toward Obama has not grown since the second round of controversy about Wright erupted last week.

Overall, Clinton and Obama remain extremely popular among Democrats, but enthusiasm for both candidates is flagging as the battle for the nomination wears on.

Holland said just one thing separates Obama and Clinton in the minds of Democratic voters -- by a 20-point margin, 57 to 37 percent, Obama is seen as the one who is more likely to become the party's standard-bearer.

Obama leads the New York senator when it comes to pledged delegates, the popular vote and states won in the primaries and caucuses held to date.

A big question facing Democrats concerns the party coming together and backing the eventual nominee. Will die-hard Clinton supporters back Obama if he's the nominee and will devoted Obama supporters get behind Clinton if she's the nominee?

According to the poll, the number of Democrats who would feel enthusiastic if Clinton were the nominee has fallen from 45 percent in January to 38 percent in March to 33 percent now. Enthusiasm for an Obama victory has also dropped, from 45 percent in March down to 36 percent now.

As for possible November showdowns with Arizona Sen. John McCain, the Democratic candidates have virtually identical but statistically insignificant advantages over the presumed Republican nominee.

Clinton and Obama both say they are more likely to beat McCain, but the poll shows each of them winning 49 percent against the Arizona senator, with Clinton topping McCain by five points and Obama beating him by four points.

The polls, however, were taken before both parties settle on a nominee and are not necessarily good indications of what will happen in November.

The CNN/Opinion Research Corp. poll was conducted by telephone from April 28-30, with 1,008 adult Americans interviewed, including 906 registered voters and 441 registered voters who describe themselves as Democrats, or as independents who lean Democratic.

The survey's sampling error is plus or minus 3 points for the overall poll and plus or minus 4.5 percentage points for the Democratic questions. E-mail to a friend

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