by Andrew Kohut, President, Pew Research Center
Special to the New York Times

As Democrats gather in Denver, many may be looking at the national polls and wondering how the presidential race has tightened so much given that voters are still concerned about the state of the nation and give low ratings to President Bush and the Republican Party. There are now at least four recent polls showing Barack Obama’s lead narrowing to three percentage points.

The Pew Research Center for the People and the Press poll last week found Barack Obama’s lead over his Republican rival withering. In late June, Obama held a comfortable eight-point margin over John McCain. A look at these latest trends suggests that while McCain has made some gains over the last two months, perceptions of Obama have stalled.

Most important, McCain has been more successful in rallying Republicans to his side than Obama has been in unifying the Democratic Party. Indeed, McCain is now garnering more support from Republicans and white evangelical Protestants than he had June, and steadily gained backing from white working-class voters over the last two months.

In contrast, Obama made little progress in increasing his support among core Democrats since June. In August, 83% of Democrats favored him compared with 87% of Republicans who back McCain. And the poll found that the presumptive Democratic presidential candidate was still getting only modest support (72%) from Hillary Clinton’s former supporters.

A second factor appears to be Obama fatigue. During the summer, the Pew Research Center’s Project for Excellence in Journalism found much more extensive media coverage of Obama than McCain. This has proved a problem, not a blessing, for the Democratic candidate.

An early August Pew survey found 48% of respondents saying they had heard “too much” about Barack Obama. Just 26% in the poll said they had heard too much about John McCain, while 38% reported that they had heard too little about the likely Republican nominee.

Obama’s extensive media exposure did not result in giving voters a fuller or better sense of who he is politically. A mid-July Pew survey found 59% of voters saying they knew little or nothing about his foreign policy positions, and 49% said the same about his economic positions. Knowledge of the Democratic candidate’s foreign policy positions was unchanged from a March poll.

Read the full commentary at nytimes.com