Sept. 25 (Bloomberg) -- Democrat Barack Obama has opened a small lead in the presidential race as his strength on the economy, the top concern of voters, outweighs Republican John McCain's advantages on Iraq and national security.

Obama leads McCain 49 percent to 45 percent among likely voters, according to a Bloomberg/Los Angeles Times national poll. The Illinois senator's edge is a little larger when minor-party candidates are thrown in, and slightly smaller among all registered voters.

The financial crisis has focused voters on economic issues, where Obama has the advantage. In addition, as has been the case all year, Obama, 47, wins higher marks on the question of which candidate would most change Washington, though Arizona Senator McCain, 72, is viewed as the most experienced.

``Obama seems to be carrying the day on the things that are important to voters,'' says Susan Pinkus, the Los Angeles Times polling director. ``It's just a matter of why isn't he further ahead.''

Democrats also retain a distinct advantage in the congressional elections. A little more than half of all likely voters say they would like to see Democrats win their congressional district, compared with 41 percent who say they plan to vote Republican.

Running Mates

The poll is the first Bloomberg/Times survey since the Democratic and Republican National Conventions in late August and early September, when both parties approved their tickets. Far more voters, 68 percent, view Obama's vice-presidential pick, Delaware Senator Joe Biden, as qualified, compared with 41 percent who say the same about McCain's running mate, Governor Sarah Palin of Alaska.

Still, slightly more voters have a positive feeling about Palin than about Biden, by a margin of 48 percent to 42 percent. This is particularly true among independents, 54 percent of whom say they have a positive view of her, compared with 30 percent who say the same about Biden.

One piece of encouraging news for the Republicans is that a bare majority of voters, 51 percent, says a McCain presidency would continue President George W. Bush's policies, a staple of Obama's campaign pitch. That is a drop from a survey in June, when 56 percent said they viewed McCain as too similar to Bush, whose approval ratings remain at historic lows.

Tax Attack

On the flip side, Republican attempts to paint Obama as a big taxer aren't resonating, either. Asked which would be more likely to lower taxes, a plurality of voters says neither; a quarter choose Obama and 19 percent pick McCain.

Obama continues to lead McCain across the board on domestic issues, which a majority of voters consider the most important factor in their choice of candidate. The Illinois senator beats McCain by 14 points on who has better ideas for strengthening the nation's economy.

In interviews, some voters say the financial system's meltdown of the past week has cemented their preferences.

``It's such a large and immediate chaos all of a sudden,'' says respondent Mike Manning, a 61-year-old federal worker from Fremont, California, who plans to vote for Obama. ``McCain has been saying that this is a hiccup and everything's going to be OK. I don't think that's going to work anymore.''

Energy, Health Care

More than half of all voters in the new poll also say they prefer Obama's plans to provide affordable health care and address the energy crisis.

On health care, Obama's proposal would offer coverage regardless of pre-existing conditions, with government subsidies for those who can't afford premiums. Just 34 percent prefer McCain's plan to give tax credits to help those who don't have employer-based health insurance to buy coverage.

When it comes to addressing soaring energy costs, 51 percent of voters say they prefer Obama's plan, which includes spending on alternative energy sources and ``green'' jobs and a proposal to give $1,000 energy rebates to working families that would be financed by higher taxes on oil company profits. McCain's plan for offshore drilling, building more nuclear power plants and a $5,000 tax credit for buying energy-efficient cars draws 38 percent support.

The poll of 1,287 registered voters, including 838 likely voters, was conducted Sept. 19-22 and has a margin of sampling error of plus or minus 3 percentage points for both groups.

Uniting the Base

Overall, it shows that both candidates have largely succeeded in unifying their party base, with 87 percent of Democrats backing Obama and 91 percent of Republicans lining up behind McCain. As in previous polls, voters show more excitement about Obama, with 84 percent of his voters describing themselves as enthusiastic, compared with 70 percent of McCain backers who say the same.

In addition, the poll shows the change message still belongs to Obama, with slightly more than half of all registered voters saying he would substantially change the way things are done, compared with 27 percent who say the same for McCain.

Yet the survey also shows Obama is still struggling to consolidate support from voters who backed New York Senator Hillary Clinton in the primary elections, about a quarter of whom say they plan to vote for McCain and Palin, 44.

One such voter is Rose Jarvis, a 46-year-old poll respondent from Ripley, West Virginia, who voted for Clinton and now backs McCain.

Jeremiah Wright

She says she has been influenced by the controversial comments of Obama's former pastor, Reverend Jeremiah Wright, and cites crime in Chicago and sex education for children, issues that have been the subject of attack ads against Obama.

``I feel I've had to give up being a Democrat,'' says Jarvis, a homemaker.

McCain's greatest area of strength in poll is the growing perception of voters that he is the best leader on national security and the war in Iraq. He leads Obama 54 percent to 29 percent when it comes to who would best protect the country from terrorism, and by 16 points on who would best achieve success in Iraq. On both questions, the Republican has wider margins of support than in the June poll.

McCain receives slightly higher ratings when it comes to the question of who Americans trust to deal wisely with an international crisis; 67 percent say they have confidence in Obama, compared with 77 percent who say they trust McCain.

Also encouraging for McCain: He may be showing some success in expanding his Republican base. Independents are supporting the Republican presidential ticket by a margin of 49 percent to 34 percent. Whites back McCain by a margin of 49 percent to 39 percent, while black voters give Obama 96 percent of their support, compared with 3 percent for McCain.

Males are slightly more likely to favor McCain; women prefer Obama. Geographically, Obama has a distinct lead in the East and West, and McCain leads in the South.

To contact the reporter on this story: Heidi Przybyla in Las Vegas at hprzybyla@bloomberg.net

Last Updated: September 24, 2008 17:00 EDT