Poll suggests presidential race can change quickly

The presidential race remains volatile and unpredictable, largely because of a huge bloc of undecided swing voters.

“The middle of the electorate is reasserting itself in this election,” according to a Pew Research Center survey released Thursday.

Among all voters, Democrat Barack Obama leads Republican John McCain by 48 to 40 percent. Pew polled 2,004 people by land line and cell phone from June 18 to 29. The margin of error is plus or minus 2.5 percentage points.

The White House hopefuls face an unusual number of variables, and as a result “the outlook for the presidential election in midyear is substantially different than at comparable points in time in recent campaigns,” the survey found.

Among those variables:

Independents make up about one-third of the electorate, and those who have preferences are split virtually evenly between Obama and McCain.

However, some 46 percent of independents are undecided or only lukewarm toward their current choices.

Both candidates “face formidable challenges in consolidating their bases.” McCain has “an enthusiasm problem” among Republicans, while Obama “has a unity problem” among Democrats.

McCain has the bigger hurdle, as Pew found that he “receives far less strong backing from his supporters.” Only 35 percent of McCain's supporters say they back him strongly, while 55 percent of Obama's voice strong support for him.

Turnout is likely to be far higher than in recent elections.

Voter interest, particularly among Democrats, continues at high levels. Younger people in particular are more interested than usual. Pew found two-thirds of 18- to 29-year-olds have given “quite a lot of thought” to the election, up from 53 percent four years ago and 35 percent in June 2000.

Domestic issues are foremost on voters' minds.

Some 44 percent said they most wanted candidates to discuss the economy, with Iraq a distant second priority at 19 percent.