WASHINGTON (Reuters) - Democratic presidential contender Barack Obama opened narrow leads on Hillary Clinton in California and Missouri one day before crucial “Super Tuesday” nominating contests in 24 states, according to a Reuters/C-SPAN/Zogby poll released on Monday.

In the Republican race, Arizona Sen. John McCain solidified his double-digit leads over Mitt Romney in New York and New Jersey, but Romney expanded his lead in California, the biggest prize on “Super Tuesday.”

Obama and Clinton were deadlocked in New Jersey, and Obama enjoyed a double-digit advantage over Clinton in Georgia in two other Democratic contests on the biggest single day of voting ever in a U.S. presidential nominating campaign.

Obama, an Illinois senator, and Clinton, a New York senator, have waged a bitter duel for the Democratic presidential nomination, competing for votes from coast to coast after splitting the first four significant contests.

“The momentum is with Obama,” said pollster John Zogby. “If this trend continues it could be a very big night for him.”

Romney, a former Massachusetts governor, led McCain 40 percent to 32 percent in California, where the margin of error was 3.3 percentage points. A win in California, the most populous state, could help puncture McCain’s growing momentum in the Republican nomination fight.

McCain won the last two contests, in South Carolina and Florida, to seize the front-runner’s slot in a hard-fought Republican race despite qualms among some conservatives about his past views on taxes, immigration and campaign finance.

“Romney is widening his lead in California and has a really big advantage with conservatives,” Zogby said. “Romney winning California would give some Republicans pause when they look at McCain as the potential nominee.”

Romney said he would cut short a scheduled trip to Georgia and fly back to California on Monday for a last-minute campaign visit.

‘A GOOD SHOT’

“People there are taking a real close look at the race and it looks like I’ve got a good shot there,” Romney told reporters.

In Missouri, McCain leads former Arkansas Gov. Mike Huckabee by 35 percent to 27 percent, with Romney in third place at 24 percent. The margin of error was 3.4 percentage points.

“Huckabee and Romney are splitting the anti-McCain vote in states like Missouri,” Zogby said.

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The Reuters/C-SPAN/Zogby rolling tracking poll surveyed presidential races in both parties in California, New Jersey and Missouri. The polls also looked at the Republican race in New York and the Democratic race in Georgia. Polling will continue for one more night.

In California, Obama gained two points on Clinton overnight to lead 46 percent to 40 percent, with a margin of error of 3.2 percentage points. Obama wiped out a 1-point Clinton advantage in Missouri to take a 47 percent to 42 percent lead, with a margin of error of 3.4 percentage points.

The two rivals were deadlocked at 43 percent in New Jersey, with 10 percent still undecided. Obama had a 17-point edge in Georgia, aided by a more than 3-to-1 edge among black voters.

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Both Democrats continued to build a strong base of support, with Clinton favored by women, Hispanics and elderly voters and Obama favored by blacks, men and young voters.

The new poll found McCain, who could be on the path to the Republican nomination with a strong performance on Tuesday, doubling Romney’s support in New Jersey and doing even better in New York.

All of the presidential contenders are aiming on Tuesday to win a big share of the national convention delegates who choose the nominees. More than half of the total Democratic delegates are up for grabs on Tuesday, and about 40 percent of the Republican delegates.

The rolling polls in all five states were taken Friday through Sunday with samples ranging from 835 likely Republican voters in New Jersey to 967 likely Democratic voters in California.

In a rolling poll, the most recent day’s results are added while the oldest day’s results are dropped in order to track changing momentum.

(Editing by Patricia Zengerle)