WASHINGTON (CNN) -- With an unpopular president and a troubled national economy, large numbers of Democratic and independent voters are increasingly calling for "change" -- and looking to Sen. Barack Obama as the solution.
But a surprising trend is emerging: Polls show a tight race between Obama and Sen. John McCain.
Asked whether they would rather see a Democrat or a Republican elected president, voters in a Wall Street Journal-NBC News Poll released July 23 said they prefer a Democrat, by 12 points: 48 percent to Republicans' 36 percent. The margin of error is plus or minus 3.1 percentage points.
But in CNN's "poll of polls" taken from July 22-27, Obama is only 5 points ahead of McCain: 45 percent to 40 percent.
So far, the election looks more like a referendum on Obama than on President Bush. Many voters simply don't know much about Obama.
McCain, meanwhile, is trying to fill in the blanks. His campaign spent about $3 million running an ad released July 21 in key battleground states.
"Some in Washington are still saying no to drilling in America. No to independence from foreign oil. Who can you thank for rising prices at the pump?" the narrator said in the ad entitled "Pump." A crowd featured in the ad chants, "Obama! Obama!"
The ads are keeping the race close.
"Negative ads make undecided voters just that more undecided, so what it can do is have a way of at least freezing the race in place," said Evan Tracey of TNS/Campaign Media Analysis Group.
The Obama campaign, however, is fighting back in an ad released Tuesday.
"John McCain is blaming Barack Obama for gas prices? The same old politics," the narrator said.
Obama is trying to avoid falling into McCain's trap.
"I think that McCain would like nothing more than to get the Obama campaign at a back-and-forth with negative ads that carries through the fall," Tracey said. "This obviously works against Sen. Obama's caricature of being a new politician."
McCain's negative strategy is keeping the focus on Obama.
By nearly 2 to 1, voters say they are paying more attention to what kind of president Obama would be than what kind of president McCain would be.
The Wall Street Journal-NBC News Poll showed that 51 percent are paying attention to Obama versus the 27 percent for McCain.
CNN political producer Ed Hornick contributed to this report.