WASHINGTON — Sen. Hillary Clinton has inched ahead of former Sen. John Edwards in a tightening Democratic presidential race in Iowa, while the Republican race is shifting in surprising ways, according to a new poll made available exclusively to McClatchy Newspapers and NBC News.
The poll by Mason-Dixon Polling and Research Inc. showed that Clinton, D-N.Y., has the support of 22 percent of likely caucus voters in Iowa, with Edwards, D-N.C., right on her heels at 21 percent. Illinois Sen. Barack Obama was third at 18 percent. New Mexico Gov. Bill Richardson placed fourth with 6 percent.
Edwards had an average 3 percentage-point lead over Clinton in Iowa last month in five national polls, with Obama an average 7 points behind Edwards.
Clinton's small lead in the Mason-Dixon poll falls within the survey's margin of error — plus or minus 5 percentage points — but indicates that support for her is growing in the state that will hold the first nominating contest for Democratic and Republican presidential candidates, on Jan. 14.
The Mason-Dixon poll also revealed some seismic shifts among Republican candidates, with one undeclared candidate gaining serious ground and two top-tier candidates slipping badly.
Former Massachusetts Gov. Mitt Romney led the field with 25 percent. Former Tennessee Sen. Fred Thompson, who has yet to formally enter the race, polled 17 percent. Former New York Mayor Rudy Giuliani had 15 percent. Former Arkansas Gov. Mike Huckabee placed fourth at 7 percent.
Sen. John McCain, R-Ariz., once considered the favorite to win the Republican nomination, won only 6 percent support from likely Republican caucus voters in Iowa, tying him with Sen. Sam Brownback, R-Kan.
McCain's fall in Iowa has been steep: He enjoyed average support of 19 percent in five national polls last month, only 1.2 percent less than front-runner Romney, according to RealClearPolitics.com. Giuliani also appears to be losing altitude; he averaged 18.6 support in five Iowa polls last month.
McCain also slipped badly in a Mason-Dixon poll of South Carolina Republicans released last weekend, to fourth place with only 7 percent support. Thompson led that poll with 25 percent. McCain's staunch support for the war in Iraq and comprehensive immigration restructuring may be weighing him down.
In addition, Dianne Bystrom, a political science professor at Iowa State University, said the shift among Republican candidates was rooted in decisions by McCain and Giuliani to bypass the Iowa straw poll in August. Romney has committed to attend the event, which is a big fund-raiser for the state Republican party.
"It had an effect on rank-and-file Republicans, and it looked to other people like they (Giuliani and McCain) are ignoring the state," Bystrom said.
Romney, meanwhile, appears to be putting a little distance between himself and the rest of the Republican contenders. He's been spending heavily on television and other advertising in recent weeks, and was widely judged to have performed impressively in two initial debates.
As for Thompson's rise, Dennis Goldford, a political science professor at Drake University, said his strong showing had more to do with the state of the Republican Party than with Thompson himself.
"Thompson is a word that politically means 'none of the above,' " Goldford said. "He's a choice of people currently not satisfied with the current field. They're looking for a Ronald Reagan."
The Mason-Dixon poll was conducted June 13-16 with 400 likely Republican caucus voters and 400 likely Democratic caucus voters.