Colorado Sen. Mark Udall will lose his tough re-election campaign to Republican Rep. Cory Gardner in November, according to Roll Call’s Stu Rothenberg, who made the prediction on CNN’s “State of the Union” Sunday.

Udall is running a neck-and-neck race with Gardner, whose decision to run for Senate in lieu of reelection to the House energized what had been a lackluster race. The high-profile duel has attracted big money from groups supporting both candidates and the issues have centered on energy and health care.

Host Candy Crowley asked her guests — in addition to Rothenberg, the panelists included Mo Elleithee of Hilltop Public Solutions and Republican National Committee spokesman Sean Spicer — to suggest something that will surprise her on the day after the election.

“I think probably Udall loses in Colorado to Cory Gardner in a race that, three months ago, you would have said is off the table,” Rothenberg replied.

The most recent poll, by American Crossroads, shows Udall with a two-point lead over Gardner. Voters polled disapprove of Udall’s job performance 46-38 percent.

Udall is believed to be vulnerable for his support of the Affordable Care Act as well as on his attempt to straddle the fence on energy issues. On one hand, he has pledged to fight climate change, a stance that has attracted him to big-money donor Tom Steyer, who has pledged $100 million for campaigns highlighting that issue.

On the other, Udall has called himself the “champion of Colorado’s natural gas industry” and proposed fast-tracking approval for liquid natural gas exports as part of an aid package for Ukraine.

The Rothenberg Political Report, last updated on March 14, shows the Colorado Senate race as leaning toward Udall. A month before, it had been rated as “Democrat favored.”

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