By Daniel Wallis
DENVER (Reuters) - What was once a "fly-over" Senate race in Colorado has become one of the nation's most closely watched contests, with a young Republican congressman who is leaving a safe seat in the U.S. House fiercely attacking Democratic incumbent Mark Udall.
As mail-in ballots headed to post boxes across the state this week, Udall's path to re-election appeared steeper after he failed to win the endorsement of the state's flagship newspaper. Polls show a race that's too close to call.
"It's a toss-up. ... There's no one single issue that defines the race," said Floyd Ciruli, a Denver-based independent pollster, adding that various polls show each candidate with a slight lead.
A poll by SurveyUSA and the Denver Post released on Monday showed U.S. Representative Cory Gardner ahead of Udall, 45 percent to 43 percent.
Democrats say Republicans have made politically purple Colorado ground zero in next month's general election as they seek to wrest control of the U.S. Senate from Democrats.
Udall, 64, is seen as potentially vulnerable because of his support for the Affordable Care Act, known as Obamacare, and because his 40-year-old rival has strong name recognition.
In a bombshell editorial on Friday, the traditionally liberal Denver Post backed Gardner, though it lauded Udall as "a fine man with good intentions."
It said Udall was not seen as a leader in Washington and complained his team spent a "shocking amount of energy and money" unfairly trying to persuade voters that Gardner wants to outlaw birth control.
"His obnoxious one-issue campaign is an insult to those he seeks to convince," the newspaper said.
Udall, who is running for a second term, has followed a well-trod tactic of Colorado Democrats by putting women's issues front and center. At a candidates' debate last week, one of the moderators noted that some pundits have dubbed him "Mark Uterus."
"If Congressman Gardner hadn't built his entire political career on limiting women's reproductive choices, we wouldn't be having this discussion today," Udall said, adding that more than half his ads have dealt with other issues.
Gardner, who is campaigning as a moderate conservative, says it is outrageous to suggest he wants to ban birth control, including over-the-counter contraceptives.
In the past, Gardner has backed "personhood" initiatives in Colorado, which defined a person as a human being from the point of conception. He says he has since changed his mind.
TRACTOR SALESMAN'S SON
So concerned are Democrats about Udall's fate that President Barack Obama urged Colorado voters to consider the race as important as the 2008 presidential battle, in which Colorado helped put Obama in the White House.
On Monday, former Secretary of State Hillary Clinton headlined a fundraiser for Udall in Denver, then posed for the cameras with the senator at the city's newly refurbished Union Station.
Democrats in the state can be vulnerable: Last year, voters recalled two Democratic state legislators who approved tighter gun laws introduced after shooting rampages there and in Connecticut. A third resigned after being targeted.
Until early this year it appeared Udall would face a Tea Party favorite, Weld County District Attorney Ken Buck. But after Gardner, a two-term congressman, said he would give up his seat in February to mount a challenge, Buck bowed out, saying he would seek Gardner's House seat.
Gardner, who represented a conservative eastern Colorado farming district, is the son of a tractor salesman. His ads have hailed his co-sponsorship of a 2007 bill to help fund clean energy projects, though critics say the bill, which was repealed five years after passage, was badly worded and ineffective.
His campaign has sounded increasingly confident since polls in September began showing him narrowly leading Udall.
Gardner has mocked Udall for skipping a Denver fundraiser led by Obama in July (Udall pleaded official duties in Washington). And in a much-talked-about TV spot, he took a jab at his rival's influential family ties.
"He's a nice guy who will never change the Senate," Gardner said. "Eighteen years in politics, and he's got two cousins who are senators too."
Udall's father, the late Morris "Mo" Udall, was a U.S. representative from Arizona who sought the Democratic presidential nomination in 1976. A cousin, Tom Udall, is a Democratic senator from New Mexico, and a second cousin, Mike Lee, is a Republican senator from Utah.
Figures released last week show Gardner out-raised Udall in the third quarter, $4.3 million to $4 million.
"Money is not the end-all," Ciruli said. "But it does show that GOP donors think this is a winnable race."
(This story has been refiled to include full name and title for U.S. Representative Cory Gardner, in paragraph four, and remove same in paragraph six)
(Additional reporting by Keith Coffman; Editing by Cynthia Johnston and Douglas Royalty)