Mr. Gore's progress in these key states reflects the bounce in national polls the Democratic presidential nominee received after his party's convention. Such a bump can be temporary but also could suggest a shift and possible rearrangement of the state electoral landscape.
California, Michigan, Minnesota and New Jersey account for more than a third of the 270 electoral votes Mr. Gore needs to win in November. The electoral math has favored Mr. Bush, the Republican presidential nominee, for months as his advantage in national polls showed up in many battleground states.
In New Jersey, Mr. Gore led 49 percent to 37 percent in the Quinnipiac Poll after Mr. Bush had pulled close in the state in recent months.
"This is probably just a spike in the horse race for Gore," said Quinnipiac political scientist Scott McLean.
He said Mr. Gore appears to have solidified his Democratic base and reached out to independents while doubling his support among Republicans to 15 percent.
In California, Mr. Gore was up 50 percent to 37 percent in a Field Poll, a margin similar to his 46-35 lead in June. A separate California poll taken between the party conventions suggested a close race.
In Michigan, Mr. Gore was even with Bush in an Epic-MRA poll taken for the Detroit Free Press with 44 percent to 42 percent for Bush, 3 percent for Green Party candidate Ralph Nader and 1 percent for Reform Party hopeful Pat Buchanan. Mr. Bush was ahead 45-37 in that same poll in early August.
Mr. Gore had a 48-40 edge in a Minnesota poll after he and Mr. Bush were tied last month.
A national poll of registered voters out Thursday by ICR of Media, Pa., had Mr. Gore at 44 percent, Mr. Bush at 41 percent, Mr. Nader at 6 percent and Mr. Buchanan at 3 percent.
"The national polls taken after both conventions are historically a pretty good guide to the general election outcome," said David Rohde, a political scientist at Michigan State University. "When the polls are very close as they are now, you would expect a very close race."
The ICR national poll of 807 registered voters was taken from Friday through Tuesday and has an error margin of 4 percentage points. The Field Poll surveyed 869 likely California voters from Friday through Tuesday and has an error margin of 3.5 percentage points.
The Minnesota poll of 621 registered voters was taken Monday and Tuesday by Mason-Dixon and has an error margin of 4 percentage points. The Quinnipiac poll of 802 registered voters was taken Friday through Tuesday and has an error margin of 3.5 percentage points. The Epic-MRA poll of 600 likely voters in Michigan was conducted Sunday through Tuesday and has an error margin of 4 percentage points.