Barack Obama took a 3 percentage-point edge over John McCain in a key tracking poll of U.S. registered voters on Monday, following a dramatic loss of the 9-point lead he gained from his well-publicized trip to Europe.

In the Gallup Daily tracking poll, voters favored Obama over McCain 46 to 43 percent. On Friday and Saturday, the poll put the two presidential candidates tied at 44 percent, and on Sunday, Obama had a 1-point lead.

The latest poll of 2,659 voters was conducted on Aug. 1-3 and has a margin of error of 2 percentage points.

Following the European trip, Obama had secured his widest lead in the tracking poll over McCain, hitting the high-water mark on July 26, the same day McCain undertook a week-long attack of Obama's celebrity status with an ad comparing him to Britney Spears and Paris Hilton.

While the ad turned off some, it hit well in other corners. The week continued with counterattacks over what the McCain campaign said was an injection of racial politics when Obama said McCain and other Republicans would start raising the issue that he doesn't look like other presidents on dollar bills. The Obama campaign criticized the McCain campaign's handling of the matter.

McCain came out with a second ad trying to paint Obama as arrogant on Friday -- drawing contrasts between lofty rhetoric and mockingly comparing the campaign to Charlton Heston's Moses -- and over the weekend, Obama switched positions on oil drilling, saying he would now be open to limited proposals for offshore drilling.

Gallup reports that the 3 percentage-point lead Obama holds over McCain matches the average he's held since he clinched the Democratic Party nomination in early June.