from Reuters

Obama had opposed new offshore drilling, but said recently he would support a limited expansion as part of a comprehensive energy program.

That was one of several recent policy shifts for Obama, as he positions himself for the general election battle. But Zogby said the changes could be taking a toll on Obama’s support, particularly among Democrats and self-described liberals.

„That hairline difference between nuance and what appears to be flip-flopping is hurting him with liberal voters,” Zogby said.

Obama’s support among Democrats fell 9 percentage points this month to 74 percent, while McCain has the backing of 81 percent of Republicans. Support for Obama, an Illinois senator, fell 12 percentage points among liberals, with 10 percent of liberals still undecided compared to 9 percent of conservatives.

OBAMA NEEDS TO WORK ON BASE

„Conservatives were supposed to be the bigger problem for McCain,” Zogby said. „Obama still has work to do on his base. At this point McCain seems to be doing a better job with his.”

The dip in support for Obama, who would be the first black U.S. president, cut across demographic and ideological lines. He slipped among Catholics, born-again Christians, women, independents and younger voters. He retained the support of more than 90 percent of black voters.

„There were no wild swings, there isn’t one group that is radically different than last month or even two months ago. It was just a steady decline for Obama across the board,” Zogby said.

Obama’s support among voters between the ages of 18 and 29, which had been one of his strengths, slipped 12 percentage points to 52 percent. McCain, who will turn 72 next week, was winning 40 percent of younger voters.

„Those are not the numbers Obama needs to win,” Zogby said about Americans under 30. The 47-year-old is counting on a strong turnout among young voters, a key bloc of support during his primary battle with New York Sen. Hillary Clinton.

It made little difference when independent candidate Ralph Nader and Libertarian Party candidate Bob Barr, who are both trying to add their names to state ballots.

McCain still held a 5-point edge over Obama, 44 percent to 39 percent, when all four names were included. Barr earned 3 percent and Nader 2 percent.

Most national polls have given Obama a narrow lead over McCain throughout the summer. In the Reuters/Zogby poll, Obama had a 5-point lead in June, shortly after he clinched the Democratic nomination, and an 8-point lead on McCain in May.

The telephone poll of 1,089 likely voters had a margin of error of 3 percentage points.

The poll was taken as both candidates head into their nominating conventions and the announcements of their choices of vice presidential picks. The Democratic convention begins on Monday in Denver, with the Republican convention opening the next Monday, September 1, in St. Paul, Minnesota.