A series of national and state polls this week presented differing snapshots of how Barack Obama is faring nationally, in swing states that have been key in general elections and in upcoming Democratic primaries. But one common denominator appears to be the challenge he faces among white voters, particularly working class white voters.

Obama has clearly sustained damage among this group after a month in which much of the campaign news was dominated by the controversy over Obama’s former pastor, Rev. Jeremiah Wright, and his “bitter” reference about small town Americans who had been suffering economically.

In a new national Pew Research Center poll conducted April 23-27, Hillary Rodham Clinton led Obama among white voters in April 54 percent to 38 percent, compared to a 44 percent tie with Obama in March.

Among whites with educations of high school or less, she led Obama 65 percent to 25 percent, a gain of 15 points over March. Among whites earning less than $50,000 a year, she led 58 percent to 34 percent, a jump of 11 points compared to a month earlier.

Pew rated the favorability of each candidate by several criteria. Obama is still viewed favorably on most counts, but his biggest decline came when voters were asked if he was “down to earth,” a measure by which he fell 9 points since March to 73 percent.

(If Obama’s challenge has been doubts among white voters about him, Clinton’s has been her consistent negative marks in polls when it comes to the “honesty and trustworthiness” question. When voters were asked by Pew to rate Clinton’s honesty, her mark fell from 65 percent in March to 57 percent in April. Thirty-five percent called her phony in April compared to 29 percent in March.)

The finding on white voters in the Pew survey was mirrored in another poll today of three states that are key swing states in general elections: Florida, Ohio and Pennsylvania.

A Quinnipiac University poll conducted April 23-29 said Clinton ran better than Obama in general election-match-ups against John McCain in those states thanks to her stronger base of support among white working class voters:

• Florida: Clinton led McCain 49 percent to 41 percent while McCain edged Obama 44 percent to 43 percent. The margin of error was 2.6 percent. Clinton tied McCain among white working class voters at 45 percent each, while McCain beat Obama in this group 51 percent to 34 percent.

• Ohio: Clinton led McCain 48 percent to 38 percent, while McCain was ahead of Obama by 43 percent to 42 percent. The margin of error was 2.9 percent. Clinton led McCain among white working class voters 46 percent to 40 percent while McCain led Obama 54 percent to 34 percent.

• Pennsylvania: Clinton led McCain 51 percent to 37 percent and Obama bested him 47 percent to 38 percent. The margin of error was 2.5 percent. Clinton led McCain among white working class voters 48 percent to 40 percent while McCain led Obama 45 percent to 38 percent.

Quinnipiac’s Peter Brown said, “There is no indication that Obama’s problems with white working class Democrats in the Ohio and Pennsylvania primaries have gone away,” and added: “If the superdelegates are looking at electability, these results could be a shot in the arm for Sen. Clinton . . . No one has won the White House since 1960 without carrying two of these three swing states.”

Three national polls released Wednesday all had at least some elements that pointed to Obama’s problem.