Independent U.S. Senate candidate Greg Orman, in July. Photograph by Charlie Riedel/AP

Last night, Chad Taylor, the Democratic nominee in the upcoming Senate election in Kansas, announced that he was dropping out of the race. This is the biggest political story of the week: the path is now clear for the independent candidate Greg Orman to run against the unpopular Republican incumbent Pat Roberts. Orman is now the front-runner, a change that puts the Democrats squarely in the driver's seat to retain control of the Senate.

Two weeks ago, I analyzed a relatively unnoticed survey result from Public Policy Polling: in a three-way matchup between Taylor, Roberts, and Orman, Roberts was in the lead, as could be expected given Kansas’ strong Republican voting base. Roberts was also the front-runner in a one-on-one matchup against Taylor. But, when Orman, a former Democrat, was matched up against Roberts alone, Orman led by a significant margin.

This curious set of results can be explained by two simple observations: Pat Roberts is incredibly unpopular in Kansas, but so is the national Democratic Party. Twenty-seven per cent of Kansans approve of Roberts's job performance; but only thirty-three per cent approve of President Obama's performance. That leaves a lot of votes up for grabs for someone who is neither a Democrat nor a Republican.

Can the survey result be explained? Yes. Imagine that the Kansas electorate is composed of four hypothetical populations:

Roberts supporters: forty-five per cent of voters. Taylor supporters whose second choice is Orman: forty-one per cent. Orman supporters whose second choice is Taylor: seven per cent. Orman supporters whose second choice is Roberts: seven per cent.

Under these circumstances, if Orman were to drop out, it would help both of the remaining candidates equally, meaning that Roberts would still be ahead. But Taylor dropping out would catapult Orman to fifty-five per cent, compared to Roberts's forty-five per cent—a lead of ten percentage points.

An Orman win could have a seismic effect on who controls the Senate. Orman says that he would caucus with the Senate's two other independents, Bernie Sanders and Angus King. Both Sanders and King currently caucus with the Democrats. To be fair, Orman is not just a Democrat in disguise–he has promised to vote out Democrat Harry Reid as Majority Leader if he gets the chance. But Orman says that he wants to break the current gridlock in the Senate, and Senate Republicans have been gumming up the works on legislation and judicial appointments. So while Orman would be far from a shoo-in to vote for every Democratic position, he would certainly not be involved in any alliances with the Republicans.

Right before Taylor’s announcement yesterday, according to data from the Princeton Election Consortium, the Democrats had a sixty-five per cent chance of retaining control of the Senate. (Polling wonks will notice that this number is significantly different than what has been put out by outlets like the Washington Post’s Monkey Cage, the New York Times’ Upshot, and Nate Silver’s FiveThirtyEight, all of whom give an edge to the Republicans. The Princeton Election Consortium, which I founded, only relies on polling data and does not factor in so-called “fundamentals,” such as campaign finances and incumbency. In the past, our purely poll-based approach has yielded extremely accurate results.) As noted here, with Orman facing off alone against Roberts, the probability of Democratic control shot up to eighty-five per cent.

During the past two weeks, polls in other states have moved even more in the Democrats' favor. It’s safe to say that thanks to Chad Taylor's decision, the Democratic Party is now the odds-on favorite to retain control of the Senate.