Fueled by voter dissatisfaction with President Barack Obama's administration and the economy, Republican Roy Blunt leads Democrat Robin Carnahan in the highly charged Missouri race for U.S. Senate, according to a Post-Dispatch/KMOV-TV (Channel 4) poll.

The poll, conducted July 19-21, asked voters if they would support Blunt, a congressman from Springfield, or Carnahan, Missouri's secretary of state. Blunt was backed by 48 percent of the respondents, compared to 42 percent for Carnahan. The remaining 10 percent were undecided.

The two are expected to sail through their party primaries on Aug. 3 and face off in the general election in November.

"Outside of the metro areas, he's killing her," said Brad Coker, managing director of Mason-Dixon Polling & Research, the firm that conducted the poll.

Carnahan leads in the more populated St. Louis and Kansas City areas, which tend to vote Democratic. But Blunt leads every other region of the state by a healthy margin, the poll found. In the Republican hotbed of southwest Missouri, where Blunt lives, the seven-term congressman leads nearly 3 to 1.

Pollsters conducted telephone interviews at random with 625 registered Missouri voters who said they cast ballots regularly in state elections. The poll has a margin of error of 4 percentage points.

Coker pointed to the unpopularity of Obama, especially among independents, as a key reason Blunt is faring better with Missouri voters. Blunt has made tying Carnahan to Obama a staple of his campaign. While the poll was in the field, he was running a television ad highlighting Obama's recent appearance at a Carnahan fundraiser.

In the poll, 57 percent of respondents disapproved of Obama's performance as president, compared to 34 percent who approved. Among independent voters - those who didn't identify themselves as Democrats or Republicans - 63 percent disapproved of Obama's performance.

Obama, who narrowly lost Missouri in the 2008 election, now has "horrible" numbers in the state, Coker said, especially compared to the rest of the U.S.

A CNN poll taken the same week as the Post-Dispatch poll, for instance, had 50 percent of national respondents disapproving of Obama's job performance and 47 percent approving. A Fox News poll a week earlier had the president's disapproval rating at 48 percent.

Coker said it's possible that Blunt's television ad skewed the Missouri results somewhat, but he said the overall unfavorable ratings voters gave to Obama - and Carnahan's lack of strength with independent voters - were stronger factors.

The poll found that the top issue on voters' minds was the economy. Government spending and health care came in second and third. Those issues simply don't line up well for Democrats this year, Coker said.

"The voters are on the Republican side on all three issues," he said.

On issues such as the economy and health care reform, poll respondents, including independents, gave the president low marks. And 78 percent of independents said the country is on the "wrong track."

By contrast, the agenda of the Tea Party movement, which generally opposes Obama's policies, was received more favorably than not, even among independents, the poll found.

In swing states such as Missouri, independents typically hold the key to deciding races.

"I'm just afraid of a Democrat right now," said poll participant Robert Young, 84, of Lebanon, Mo., an independent who has voted for Democratic candidates in the past.

Young said he opposes efforts to cap carbon emissions, which Republicans have criticized as an energy tax, and fears Obama is "building his own little dynasty."

Carnahan and Blunt are jockeying for the right to replace outgoing Sen. Christopher "Kit" Bond, a Republican. The only other primary candidate to receive double-digit support in the poll was state Sen. Chuck Purgason, though he lagged far behind Blunt among Republican voters.

Blunt and Carnahan have each raised more than $3.5 million in the race. The two candidates are well-recognized by voters after years in public life. Both have near 100 percent name identification in the state, according to the poll.

Of those voters who recognize them, both were found to be "favorable" by 39 percent of the poll respondents. But Carnahan's "unfavorable" ratings were much higher than Blunt's: 38 percent to 23 percent.

Before his time in Congress, which included a stint in Republican leadership, Blunt was Missouri's secretary of state, president of a Baptist university in southwest Missouri and county clerk in Greene County. His son, Matt, was governor.

Carnahan's family political legacy goes back several generations. Her father, Mel, was the Democratic governor who died in a plane crash while running for U.S. Senate. Her mother, Jean, filled that Senate seat after the Carnahan win, and her brother, Russ, is a Democratic congressman from St. Louis.

Poll respondent Debbi Whetton, 56, of Creve Coeur, supports Carnahan but believes she is relying too much on her family background to court voters.

"She needs to get out there more," Whetton said. "It almost sounds like she's just running on her name, which is kind of sad."

Multiple generations of office-seekers can lead to confusion.

One poll respondent said he respected Blunt because he served in the Navy - although it was his son Matt who served. A Carnahan supporter had the candidate confused with her mother, who served in the Senate from 2001-2002.

"The Carnahan name is one that is familiar to me, all the way back to Mel," said Theresa Klipfel, 60, of Wentzville, who is supporting Robin Carnahan.

Blunt's lack of negative ratings by voters is in stark contrast to poll respondents' views on Congress. Nearly 80 percent of poll respondents had an unfavorable view of Congress, where Blunt has served for 14 years.

Terry Jones, a political science professor at the University of Missouri-St. Louis, says the Post-Dispatch/KMOV-TV survey matches similar polls that showed Blunt with a small lead.

Jones, however, found in the latest results some reasons for Carnahan to be optimistic. Many independents, who typically don't begin paying attention to the race until much later, can still be swayed. Blunt has not been able to cross the key threshold of 50 percent in any major published poll, Jones said.

And, given Obama's poor approval ratings in Missouri, Carnahan should be pleased she is not lower in the poll, he said.

"If you'd ask me to put odds on it, I would say, given these numbers, Blunt would be a slight favorite," Jones said.

But if past Senate races in Missouri are any indication, the Blunt-Carnahan matchup will be decided by a small margin.

No one knows that better than current U.S. Sen. Claire McCaskill, a Democrat, who defeated then-incumbent Jim Talent, a Republican, by less than 2.5 percentage points in 2006. Jean Carnahan lost to Jim Talent in 2002 by just more than 1 percentage point.

"This is going to be a nail-biter race - as they typically are," McCaskill said. "When I first came to Washington, I won an amendment by two votes. One of the older senators made fun of me and said, ‘That was a close call; it was only two votes.' And I said, ‘You know in Missouri, Senator, we call that a landslide.' "