WASHINGTON -- More than half the states holding presidential contests next month on Super Tuesday allow unaffiliated voters to participate, giving millions of independents a chance to shape what is usually an insider affair among Democratic and Republican loyalists.

Two of those states -- California and New Jersey -- together have nearly 6 million unaffiliated voters who will be allowed to cast ballots. Georgia, Illinois, Massachusetts and Alabama are among other prized catches with millions of independents eligible for the Feb. 5 contests.

The open voting is widely considered to benefit Democratic Sen. Barack Obama and Republican Sen. John McCain, who have fared well among independents in recent polls and primaries. It also is reflected in Obama's words, from his outreach to Republican voters to his recent credit to Ronald Reagan in the context of elections that represent shifts in political direction.

"Obama's trying to do two things at once. On the one hand, energize the liberal base, but also attract independents who are looking for a bipartisan problem-solver," said Jack Pitney, a former deputy research director for the Republican National Committee and a government professor at Claremont McKenna College in California. "That's a very difficult balance, and [Hillary] Clinton is trying to highlight the contradiction there."

Pitney and others said turnout will probably be high among independents because of the wide-open contests in each party. But it's tricky to predict the effect, they said.

Independent appeal

In winning South Carolina's primary Saturday, for example, Obama drew 42 percent of voters describing themselves as independents, compared with 26 percent for Democratic rival Hillary Rodham Clinton, according to exit polls.

But he had similar advantages among independents in New Hampshire and Nevada, and lost both states as Clinton won stronger support from core Democrats.

"It makes a difference at the margin," Pitney said. "I don't know of any cases where independents by themselves have decided a nomination, but in a very close contest, they might be able to tip it one way or another."

Fifteen of the 24 states holding contests on Super Tuesday have some form of flexible voting system. Some are wide open, allowing voters to cast ballots in either party regardless of political affiliation. Others have semi-open primaries, allowing unaffiliated voters to participate if they register with a party on the day of the primary.

Obama could get the biggest boost, analysts said, because independents appear to be leaning toward Democrats this year.

Six in 10 opted to participate in the Democratic contest in New Hampshire's open primary. In exit polls, they have expressed dissatisfaction with President Bush and the war in Iraq, as well as strong concerns about the economy.

McCain's fortunes

Among Republicans, McCain has continued to attract independent voters as he did against George W. Bush in 2000, but they haven't turned out as strongly.

In winning South Carolina's GOP primary on Jan. 19, McCain took 42 percent of the unaffiliated vote to Mike Huckabee's 25 percent. But those voters made up only 18 percent of the electorate, compared with 30 percent in 2000.

Another potential pitfall for McCain is that in California -- which has more delegates than any other state -- independents will not be allowed to participate in the GOP primary because party leaders decided to close their contest, while Democrats are keeping theirs open.