* White voter pool still the largest, but shrinking
* Romney needs to improve on McCain's support among white men
* White voters fled Democrats in 2010 elections
By Samuel P. Jacobs
WASHINGTON, Oct 11 (Reuters) - With the race between Mitt Romney and Barack Obama tightening, the Republican needs one group more than any other to drive him to the White House: white men.
For Romney, the support of white male voters offers the likeliest path to the presidency, even as betting on white men is proving an increasingly risky proposition for Republicans.
His reliance on that voter group becomes more acute as polls show him far behind with African-Americans, lagging badly among Hispanics, and at a disadvantage with women in many polls, despite overall poll numbers showing him essentially tied with Obama in recent days.
Ninety percent of Republican voters were white in 2008, according to exit polls, while white women tend to be more evenly split between the two parties.
The bulwark of white male support is slowly eroding. For decades, each presidential election has offered a smaller pool of white voters. That puts pressure on Romney to secure a greater share than previous Republican presidential nominees of the shrinking proportion of the electorate made up by white men.
Adding to Romney's electoral challenge: white male voters are more conservative and describe their views in ways increasingly different from the rest of the population, according to Reuters/Ipsos polling. That trend stretches a candidate who must simultaneously retain his base and increase the diversity of his supporters.
White male voters currently pose challenges for both campaigns. A smaller percentage of likely white male voters said it preferred Obama than voted for him in 2008. At the same time, a smaller percentage of white male voters also favors Romney than it did John McCain in his losing effort four years ago.
If Romney does not improve on McCain's performance among white men, the electorate's second largest voting demographic after white women, he will likely repeat McCain's fate, pollsters and demographers said. Obama faces similar odds: a huge dip in white male support could spell the end of his time in office.
According to Reuters/Ipsos polling conducted Oct. 1 to Oct. 7, likely white male voters favored Romney 55.5 percent to 31.9 percent. Six percent of likely male voters said they were undecided.
Romney's advantage over Obama exceeds McCain's, but falls short of his fellow Republican's total share of the white male vote. In 2008, McCain outpaced Obama among white male voters 57 percent to 41 percent, according to exit polls.
"The fact that (Romney) is right in line with McCain does mean he has work to do," said Ipsos pollster Julia Clark.
PRESSURE ON OBAMA TOO
In 2010, whites fled from Democratic candidates. White voters supported Republicans 60 percent to 38 percent in the midterm elections, according to exit polls. In 2006, Republicans held only a 4-point advantage among white voters.
For Democrats, who count on consistent support among Latinos and overwhelming support among blacks, a 22-point disadvantage among white voters will not be as daunting in the future. The share of white voters in the electorate continues to slide. When Republican Ronald Reagan was elected in 1980, 89 percent of voters were white. By 2008, that figure had fallen to 73.4 percent.
Contributing to the decline in the share of white voters is the burst in eligible Latino voters. Hispanics saw their number of eligible voters increase 21.4 percent from 2004 to 2008, nearly five times the rate of growth of eligible voters in the general population, according to the Pew Research Center.
But for now, white men outnumber all minorities put together, and Obama and Romney in recent weeks have crisscrossed Ohio and Iowa as the candidates and their surrogates blanket coalfields and automobile factories hoping to lure male support in predominantly white places.
Of course, gender and race offer only a simplified snapshot of the electorate. For instance, Obama leads among likely white male voters aged 18 to 29, according to Reuters/Ipsos polling The president's advantage over Romney falls within the poll's margin of error.
The fathers and grandfathers of those young men greatly favor Romney: likely white male voters over 60 preferred the former Massachusetts governor to Obama by 62 percent to 26.3 percent during the week ending Oct. 7.
"Older white men are the people (Romney) has to turn out," said William Frey, a demographer with Brookings Institute.
WHITE MEN AND WOMEN SPLIT
White men find themselves parting not only from how minorities vote but from white women.
In Reuters/Ipsos polling ending Sept. 30, 36.5 percent of white men said the Republican Party better served the middle class, while 32.8 percent said the Democrats did.
That advantage flips when white women are polled. They give Democrats a nearly 5-point advantage over Republicans when it comes to the middle class. Minorities say Democrats serve the needs of middle-class Americans by a margin of nearly 40 points.
While white men picked Romney over Obama as the candidate with the right values by 43.5 percent to 31.4 during the week ending Oct. 7, white women showed greater ambivalence, giving the advantage to Romney 37.9 percent to 33.1 percent.
Minorities give Obama a nearly 50-point advantage on the question.
Such numbers help explain the Republican Party's dedication to showcasing leading minority and female lawmakers and candidates at the party convention in August. It also underscores how dependent Romney is on turning out white men at the polls.
While Obama bettered McCain among blacks by 90 percentage points, African-Americans accounted for 12 percent of voters in 2008, according to exit polls. There were more than six times as many white voters as black voters four years ago.
Hispanic voters turned out for Obama by a 2-to-1 margin. They accounted for less than 10 percent of voters.
Given those numbers, the growth in minority populations could be a boon for future Democratic candidates, but its benefit is unlikely to prove decisive in 2012.
The good news for Obama supporters hoping demographic change will overcome the struggling economy: Obama starts from a position of strength. His performance among white men, feared as a possible weak spot for the first African-American major party nominee, was impressive in 2008, netting 41 percent of white male voters, Obama outperformed every previous Democratic nominee since Jimmy Carter.
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