Polling may not appear to be relaible at times but it is, in fact, a science using both statistical analysis and social science to try and determine what the electorate is thinking at any given moment.

There are many reasons polls differ wildly. Different weighting being given to the same group is one big reason. If one poll directs 35% of its interviews to self-described Republicans while another interviews only 27% of Republicans, there is an attempt by the pollster to "weight" the average by using other polling data on party ID to try and get an accurate picture of the electorate. It may sound like a guessing game but the practice is rooted in solid science and is accepted as such.

Yesterday, CBS-New York Times released a poll showing Barack Obama comfortably ahead of John McCain 51-40. It also showed that the Wright controversy did not affect people's opinion of Obama.

Today, USA Today-Gallup released a poll showing that Obama's credibility had been damaged among voters as a result of the Wright controversy:

 

The Wright controversy has been especially problematic for Obama's campaign because it has helped shape Americans' emerging assessments of the candidate. In the USA TODAY survey:

• Obama's unfavorable rating climbs to a new high, 37%. His negative rating among independents, usually the swing voters in national elections, jumped from 27% in February to 36% now.

Even so, Obama's favorable-unfavorable rating of 58%-37% remains more positive than Clinton's 52%-45%. McCain's standing is the strongest of all: 62% favorable-30% unfavorable.

• One in four Americans who are following the controversy say their "best guess" is that Obama agrees with Wright's views, even though the senator has said repeatedly he finds them offensive and wrong.
• Obama has lost the 8-point advantage he held over Clinton in February as someone who "shares your values." Clinton has a 5-point edge among Democrats and Democratic-leaning independents.

The one measure on which Obama continues to hold an edge over Clinton is as someone whom Americans see as honest and trustworthy. He had a 13-point advantage in February, a 14-point edge now. "Through some weeks when the news has hardly been all positive" for Obama, "it's clear that voters trust" him, campaign spokesman Bill Burton says. "And we remain ahead in the most important measure in the Democratic nomination race, the race for delegates."

PICK YOUR POLL - These headlines initially look like they tell opposite stories, but the polls have the same message: The Wright effect has been CORROSIVE but not CATASTROPHIC.

-N.Y. Times A1, 'In Poll, Obama Survives Furor, But Fall Is Test,' by Adam Nagourney and Marjorie Connelly: 'A majority of American voters say that the furor over the relationship between Senator Barack Obama and his former pastor has not affected their opinion of Mr. Obama, but a substantial number say that it could influence voters this fall should he be the Democratic presidential nominee, according to the latest New York Times/CBS News Poll. ... [N]early half of the voters surveyed, and a substantial part of the Democrats, said Mr. Obama had acted mainly because he thought it would help him politically, rather than because he had serious disagreements with his former pastor. ...

'[T]he survey suggested that Mr. Obama ... had lost much or all of the once-commanding lead he had held over Mrs. Clinton, of New York, among Democratic voters on the question of which of them would be the strongest candidate against Mr. McCain, of Arizona. In February, 59 percent called Mr. Obama the stronger candidate, compared with 28 percent who named Mrs. Clinton. In the latest survey, the two were essentially tied.'

-USA Today, 'Poll: Flap over pastor hurts Obama,' by Susan Page: 'Barack Obama's national standing has been significantly damaged by the controversy over his former pastor, a USA TODAY/Gallup Poll finds, raising questions for some voters about the Illinois senator's values, credibility and electability. The erosion of support among Democrats and independents raises the stakes in Tuesday's Indiana and North Carolina primaries, which represent a chance for Obama to reassert his claim to a Democratic nomination that seems nearly in his grasp. A defeat in Indiana and a close finish in North Carolina, where he's favored, could fuel unease about his ability to win in November. Such results also could help propel Hillary Rodham Clinton's uphill campaign all the way to the Democratic convention in August.

'In the USA TODAY survey, taken Thursday through Saturday, Clinton leads Obama among Democrats and Democratic-leaning independents by 7 percentage points, the first time in three months she has been ahead. Two weeks ago, before the controversy over comments by Jeremiah Wright reignited, Obama led by 10 points.'