Even as the GOP’s prospects in key Senate races like Alaska, Arkansas, and Louisiana improve, the party’s chances of retaking control of the upper chamber of Congress are, by some estimates, diminishing. Why? A sizable minority of Kansas Republicans seem squarely committed to backing Democrat-turned-independent Greg Orman over incumbent Sen. Pat Roberts (R-KS).

Before today, after the state’s Supreme Court ruled that the Democratic nominee for U.S. Senate could be removed from the November ballot, no public poll released since mid-September has shown Orman leading Roberts by less than 5 points. An NBC News/Marist Survey released this week showed Roberts trailing Orman by a whopping 10 percentage points.

Real Clear Politics shows Orman ahead of Roberts by an average of precisely 5.0 percent. Ace of Spades Decision Desk essentially concurs, with Orman leading Roberts by an average of 5.4 percent support.

Few polls have released their breakdowns, but a recent Survey USA poll helped clarify where Orman’s broad base of support is coming from. Of course, for a state which has not sent anyone but a Republican to the Senate since 1932, any candidate seeking to represent Kansas in the upper chamber must secure the backing of a broad swath of the state’s GOP electorate. Orman may have done just that.

According to the latest SUSA poll, Roberts has the backing of less than two-thirds of Sunflower State Republicans. SUSA found 27 percent of self-identified GOP voters are backing Orman. 75 percent of the Kansas electorate identifies as “conservative” rather than “liberal” or “moderate.” Of those self-described conservative voters, 17 percent are supporting Orman.

“Whether the 17% of conservatives who today tell SurveyUSA they will vote for Orman stay home on Election Day, or do something else on Election Day, may well determine the outcome of the contest,” SUSA’s release noted. Likewise, if Roberts cannot secure at least 80 percent of the Republican vote in this deep red state, he probably cannot win in November.

Why so many of Kansas’s GOP voters are backing Orman at this stage remains a mystery. Nearly a month has elapsed since Orman became the de facto Democratic candidate, which should have been plenty of time to define him as slightly more left-of-center than he would prefer to cast himself.

Orman confirmed in a debate against Roberts on Wednesday that he would likely support President Barack Obama’s nominees – Republicans would like nothing more than to block as many of Obama’s appointees as they can if they were again in the majority in the Senate. In that same debate, he said that the desire on the right to repeal the Affordable Care Act is a “false choice,” and that the law should be amended.

Orman has promised that he would only caucus with the party which wins an outright majority of Senate seats, framing himself as a true independent in spite of the unfeasibility of this claim. According to Nate Silver, however, in the event Orman is in a position to determine control of the Senate (with Republicans winning 50 seats to Democrats’ 49), there is a 75 percent chance that the former Democrat would cast his lot in with Sen. Harry Reid (D-NV).

FiveThirtyEight’s Harry Enten, however, urges caution. He noted on Wednesday that there is an unusually high number of undecided voters for this late date. Moreover, the fluidity of this race suggests that the dynamics that will determine who Kansas voters send to Washington are still congealing.

“We’re only a month into this campaign, and the race is still developing,” he wrote. “We can see this by looking at the Marist poll. Only 43 percent of Kansas voters strongly supported their preferred candidate in Kansas. In Kansas’s gubernatorial race, it’s 55 percent. In Iowa’s Senate race, which Marist polled at the same time as the Kansas election, 57 percent of voters strongly supported their choice. In North Carolina’s Senate race, it’s 50 percent of voters.”

“There are more voters unattached to major candidates in Kansas than in the average competitive race,” he added, citing FiveThirtyEight’s vote-share model. Today, a CNN/ORC poll found that, without those undecideds, Roberts surges into a statistical tie with Orman. At 49 to 48 percent backing Roberts, this poll is the first lead the incumbent has enjoyed since mid-September. Roberts can attribute his lead in that poll to his ability to secure the support of 84 percent of the state’s Republican electorate and 80 percent of conservative Kansas voters.

But one poll does not a trend make, and the GOP establishment is clearly concerned that Roberts will be unable to seal the deal with his state’s voters by the first week in November.

With prominent Republicans barnstorming the state in support of Roberts, and ad spending on the incumbent’s behalf with the aim of casting Orman as less the independent that he claims to be likely imminent, it is hard to believe that the challenger will emerge on November 4 with the support of nearly 30 percent of Republicans. If he does, however, Orman will head to the Senate in January.

There will be a lot of irony in the fact that Orman, who could only have become a U.S. Senator with the support of a significant number of Republican voters, will be the figure who robs the GOP of their last, best chance to retake the Senate.