All year, Democratic strategists have considered Sen. Mark Udall as one of the strongest of their endangered incumbents. President Obama carried Colorado twice, and Sen. Michael Bennet, chair of the party's Senate campaign committee, won his Colorado seat in more difficult political circumstances for Democrats in 2010.
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Recent public polls here, however, have shown Republican Rep. Cory Gardner taking a narrow lead. The same has occurred in Iowa, another state Obama carried twice, as Republican Joni Ernst has made headway against Democratic Rep. Bruce Braley.
It's not clear how significant those movements are. In Colorado, Democrats say they reflect Gardner solidifying support from men who were always likely to back him, and that Udall continues to hold the upper hand with women voters who will eventually decide the outcome. Republicans say they reflect a backlash from voters tired of Udall's incessant focus on social issues such as abortion and contraception.
Gardner has tried to neutralize Udall's attacks on those issues. Like Republicans in other states, he backs the over-the-counter sale of birth control pills as a way to reassure undecided moderates. He has renounced his past support of a "personhood" amendment to the Colorado Constitution meant to outlaw abortion.
In other ways, too, he has taken politically cautious campaign-season stances meant to temper his earlier reputation as a partisan ideologue.
Unlike some fellow House Republicans, he doesn't quarrel with President Obama's decision to rule out combat forces in Syria, reasoning that the public is opposed. Nor does he join colleagues who vow to challenge a potential Obama executive action to legalize millions of undocumented immigrants, calling that "a hypothetical" and calling for compromise on immigration. What's not hypothetical is that Colorado has a large Latino constituency.
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Gardner's careful tightrope-walk—attempting to mobilize his conservative base while courting swing voters—contrasts with the clumsy style that caused Republican candidates to lose winnable red-state races in 2010 and 2012. Repeated elsewhere, it's why Republicans have improved their chances of a Senate takeover this year.
But all sides agree that the Colorado race remains winnable for either side. The same is true of the national contest.
The outcome hinges on turnout, and late decisions by a bloc of undecided voters representing roughly 15 percent of the electorate. Their preferences have been weak and wobbly, and may keep wobbling throughout the final weeks. And they don't like either party—which is why no one can yet predict what kind of Senate Obama will end up with.