WASHINGTON (CNN) -- The Republican presidential field appears to face a tough general election fight in a CNN/Opinion Research Corp. poll released Saturday.
John McCain was the most favorably viewed of any GOP candidate, a poll found.
According to the survey, both of the Democratic front-runners, Sens. Hillary Clinton of New York and Barack Obama of Illinois, hold mostly double-digit -- and statistically identical -- advantages over Republican presidential candidates Mitt Romney, Rudy Giuliani and Mike Huckabee, drawing greater than 50 percent support in each hypothetical matchup.
The Republican candidate who gives Clinton and Obama the closest race in the new poll is Arizona Sen. John McCain, who is essentially tied with both: He draws the support of 48 percent of those surveyed to Clinton's 50 percent and Obama's 49 percent.
Clinton leads the front-running candidates of both parties -- Obama, McCain, Giuliani, Huckabee and Romney -- in the percentage of voters who say they would definitely vote for her if she won her party's nomination, with 37 percent. But she trails the pack in the percentage of voters who do not support her, but say they might consider voting for her under those circumstances, with 19 percent.
Obama is second to Clinton in potential voters who say they would definitely vote for him in the general election, with 30 percent. McCain, who is third in that category with 22 percent, is first among voters who say they'd consider voting for him if he were the Republican nominee, with 35 percent.
The poll contained some worrying news for Romney: 62 percent of those surveyed say they will definitely not vote for the former Massachusetts governor in the general election, compared with just 13 percent who say they will definitely support him -- the worst showing of any of the major candidates.
The poll also suggests that two of his GOP primary opponents might also face an uphill climb this fall, with more than half of those polled saying they would definitely not vote for either man in November: 55 percent said they would not consider backing Giuliani, and 52 percent said the same of Huckabee, a former governor of Arkansas.
Just one other candidate in the race, McCain, competes with Obama in both categories, with a favorability rating of 54 percent and an unfavorability rating of 29 percent. McCain is the only Republican included in the poll with a favorability rating of greater than 50 percent.
McCain's closest GOP competition in the favorability category appears to be Giuliani, former New York City mayor, at 46 percent favorable to 39 percent unfavorable. In the unfavorability category, Mike Huckabee is viewed negatively by just 30 percent of those polled -- but viewed positively by just 38 percent. One-fifth of those polled have no opinion of the former Arkansas governor.
The Republican Party seems to have made a bit of a comeback from a June poll that found it was viewed unfavorably by 53 percent of the country, though more Americans still say they have an unfavorable than a favorable view of the party, 48 to 41 percent. The numbers for the Democratic Party are 55 percent favorable and 34 percent unfavorable, also a slight improvement over their June showing, 51 percent favorable and 38 percent unfavorable.
The telephone survey of 1,033 Americans, including 840 registered voters, was conducted January 9-10, and has a margin of error of plus-or-minus 3 percentage points. The hypothetical matchup results came from the registered voters; that poll had a margin of error of plus-or-minus 3.5 percentage points. E-mail to a friend 
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