A heartland contest between an embattled Republican incumbent and an upstart challenger could decide whether Democrats lose control of the U.S. Senate

Republicans need to net six seats to take over the Senate, and in recent days, Kansas appears to have moved from leaning in independent candidate Greg Orman’s favor to a toss-up that could give Republican Pat Roberts a fourth term.

Sens. Ted Cruz, R-Texas, and Tom Coburn, R-Okla., are among Roberts’s conservative colleagues who now are moved to help him keep his seat. Both  traveled to Wichita on Thursday to tell voters how much they need him.  “If you are frustrated with Washington, the answer is not to empower the liberal Democrats,” Cruz told the crowd.

Here are four things to know about the suddenly competitive race in the Sunflower State:

1.  On Oct. 1, the number of candidates officially dropped from three to two.

In a ruling pegged as a boon to Orman, a three-judge panel of the Shawnee County District Court said the Democratic Party of Kansas wouldn’t have to nominate a replacement candidate for the Senate seat.

With “underfunded” Democratic nominee Chad Taylor off the ballot and no legal cause to replace him, the race solidified as a Roberts-Orman showdown. Taylor had withdrawn from the race in September, and Republicans protested when Democrats decided to leave his place on the ballot blank.

The Kansas City Star reported that Taylor was expected to split votes with Orman, 45, giving the edge to Roberts, 78. So the court ruling was seen as a win for Democrats — with whom Orman, a multimillionaire businessman, seems more comfortable.

2. Orman looked to be way out in front of Roberts. But not anymore.

Throughout September, the race leaned heavily in Orman’s favor. An NBC News/Marist poll put Orman, born in Minnesota, 10 points ahead of the three-term incumbent Republican moving into October.

However, less than a month before Election Day, polling shows Roberts, born in Kansas, making a comeback and the race tightening. Two of the latest polls, from CNN and Fox News, show Roberts ahead by one point and five points, respectively. Both the New York Times and left-leaning Daily Kos reported shifts toward Roberts.

3. Roberts called into question Orman’s party affiliation — he says he is an independent — during last night’s debate in Overland Park.

Although Orman is running as an independent and refuses to say which party he would vote with if elected, Roberts pegged his competitor as a Democrat.

“This man is a liberal Democrat,” Roberts  said during the debate. “He will say otherwise, but that’s not the case.”

Roberts wondered aloud who Orman would support for Senate majority leader — Orman said either Sen. Lisa Murkowski, R-Alaska, of Alaska or Sen. Heidi Heitkamp, D-N.D. — what committees he would serve on and which party he would caucus with.

“Who will he vote for?” Roberts asked with a mocking tone. “He’s just one independent who’s just going to vote for people who have good ideas. That’s rather ridiculous.”

Orman argued that his past campaign donations include Republicans and Democrats. He was an early supporter of President Obama but also contributed to the first Senate bid in Massachusetts of Scott Brown, the liberal Republican now running for Senate in New Hampshire.

After the debate, CNN correspondent Dana Bash pressed Orman on which party he would vote with if elected.

“I sort of reject the premise of that question,” Orman said. “I think it’s a great thing for Kansas. I think it’s an opportunity for Kansas to define the agenda in the United States Senate.”

4. Both candidates distance themselves from Majority Leader Harry Reid.

During last night’s debate, Roberts and Orman agreed on one thing: Nevada Democrat Harry Reid’s tenure as head of the Senate should end.

“The Senate is being run poorly,” Orman said. “Harry Reid is running it like a dictatorship.”

However, Roberts and Orman each fought off attempts to link the other with President Obama and Senate leadership. Roberts said:

My opponent will do nothing to roll back Obamacare. He will do nothing to stop Barack Obama or Harry Reid, the very people he has contributed to and voted for. In fact, a vote for Greg Orman is a vote to hand over the future of Kansas and the country to Harry Reid and Barack Obama.

For his part, Orman worked to tie his opponent to Senate Minority Leader Mitch McConnell, R-Ky.:

Pat Roberts will repeatedly tell you that President Obama and Harry Reid are the reasons Washington is such a mess. And you know what? He’s half right. But the other half of the mess: Mitch McConnell and Pat Roberts.