LOWELL, Massachusetts (Reuters) - Mary Burns has the kind of Democratic pedigree that dominates Massachusetts politics. Her family and friends vote Democratic, and she lives in a district that has not elected a Republican in 35 years.

Democratic presidential candidates (L-R) Senator Barack Obama (D-IL), former Senator John Edwards (D-NC), Representative Dennis Kucinich, (D-OH), and Senator Hillary Clinton (D-NY) pose for photographers before their debate at Dartmouth College in Hanover, New Hampshire September 26, 2007. REUTERS/Lisa Hornak

But on October 17, she joined other disgruntled Democrats, voting for a Republican in a special congressional election.

Her candidate, Jim Ogonowski, who campaigned as an anti-immigration crusader, lost to Democrat Niki Tsongas by only 45 percent to 51 percent, a much closer margin than expected in a district Democrats saw as safely theirs.

Now political strategists across the country are trying to figure out what Ogonowski’s strong showing means for the nation as a whole and how worried Democrats should be about next year’s elections for president and Congress.

Despite President George W. Bush’s low poll standing, the unpopularity of the Iraq war and the formidable money advantage Democrats have established over their Republican rivals, last week’s vote warned Democrats not to get overconfident.

“There’s a lot they still have to be nervous about,” said Julian Zelizer, a history and public affairs professor at Princeton University.

“The shakiness of this particular victory in Massachusetts is the kind of thing that sends a message to the national leadership as they start to think about the next cycle.”

Democrats should remember that the Iraq war will not be the only issue in 2008 and that the party’s stance on immigration in particular -- most favor allowing illegal immigrants a path to legal status -- could be an Achilles heel, he added.

Ogonowski, a retired Air Force lieutenant colonel and brother of an American Airlines pilot killed in the September 11 attacks, was never expected to threaten Tsongas, widow of Sen. Paul Tsongas, in a district her late husband once represented.

Former President Bill Clinton and House Speaker Nancy Pelosi campaigned with Tsongas. For some voters, their presence reinforced her image as a Washington insider. Ogonowski downplayed his Republican ties and instead vowed to fix a “broken Congress” and fight illegal immigration.

While Tsongas tried to make the election a referendum on Bush and the war, Ogonowski issued fliers that overlapped images of Tsongas and Bush with the words “Niki Tsongas/George Bush Immigration Plan: Amnesty to 12 million illegal immigrants.”

‘ONE OF US’

“He was like one of us,” Burns said of Ogonowski.

“He wasn’t from a political background or a political family. He was just looking for changes in Washington like we all are. I have a lot of Democratic friends who voted for him because he understood their concerns,” the 46-year-old advertising executive added.

Some Republicans also drew confidence from Saturday’s election of Republican U.S. Rep. Bobby Jindal as governor of Louisiana. The incumbent Democratic governor, Kathleen Babineaux Blanco, still blamed for post-Hurricane Katrina incompetence, decided not to seek re-election.

“Jindal walked away with that race,” said Democratic pollster Dave Beattie, who is not affiliated with a campaign.

“There’s a real anti-incumbent, anti-Washington mood out there,” he said. “Democrats cannot take for granted that just because voters are upset with the Republican administration it doesn’t mean they think Democrats are much better right now.”

Republican pollster Tony Fabrizio said overconfidence was a risk for both parties. He recalled that many Republicans never imagined they could lose control of both houses of Congress last year.

“While there is no question that the current political environment nationally looks to benefit Democrats, it is over a year before anybody will actually go and vote. A year is an eternity in politics,” he said.

“Think back a year ago. A year ago there were still a number of Republicans who were convinced that we weren’t going to lose the House or the Senate. So many things can change over the course of year,” said Fabrizio, who is not affiliated with a campaign in 2008.