What will happen on Election Day? 5 scenarios for the Senate.

The races for US Senate still remain so close that political analysts see no fewer than five possible outcomes after polls close Tuesday. For instance, Republicans might net the six seats they need to retake the Senate. Or, Election Day might end in a state of suspended animation as candidates head to a runoff or recount. 

And one man in Kansas, independent Greg Orman, may hold the key to everything.

Here are five scenarios for today’s Senate races, and what they might mean for the next two years of governing – until America does this all over again in 2016.

A clean, GOP sweep. The minute after Republicans take the Senate, thoughts will turn to the next election. This is probably the biggest factor determining whether a GOP-controlled Congress and President Obama will cut a few modest deals – say in energy, trade, or infrastructure – or cut each other out.

“As soon as the last votes are counted, people are going to be looking ahead two years,” says John Pitney, a congressional expert at Claremont McKenna College in Claremont, Calif.

Republican leaders in the Senate and House know it will be helpful to show they can govern if they want to win the presidency in 2016 and also hold Congress – particularly the Senate, where GOP incumbents in blue states will be vulnerable two years hence. Mr. Obama, too, has his legacy to consider. This argues for dealmaking.

But three Republican senators are eyeing the presidency, including tea party favorites Ted Cruz of Texas and Rand Paul of Kentucky. Senator Cruz has already indicated he wants to show sharp contrasts with Democrats – to parade GOP colors, not compromises. House tea partyers may also gain some members as a result of today’s election.

Democrats, meanwhile, could decide they have a strong campaign theme in keeping Republicans pinned under the “Party of No” label, and they may actively work to keep them there.

Both parties could end up blocking as well as cooperating. But don’t expect anything big in the way of domestic legislation, says Mr. Pitney. Congress is still highly polarized, it still takes 60 votes to overcome a blocking filibuster in the Senate, Obama is entering his lame-duck phase, and there’s a presidential election on the way.

A big muddle. It’s likely that Louisiana will head to a runoff election on Dec. 6 and quite possible that Georgia will, too – on Jan. 6. Alaska may need a lot of time to count votes from far-flung locales and candidates who lose by razor-thin margins may contest outcomes.

The immediate impact will be on the upcoming lame-duck session of Congress, which begins Nov. 12 and is meant to complete the unfinished business of the present Congress.

Given the uncertainty over which party will ultimately control the Senate, “it’s very difficult to imagine that anything will get done in the lame-duck session” except essential business, such as passing an overall appropriations bill to avoid a possible government shutdown, says Jim Manley, former aide to Senate majority leader Harry Reid (D) of Nevada.

That will please minimalist-government senators such as Cruz, but disappoint those who may have wanted to use the lame duck as an opportunity for one last push for bigger things – such as a highway funding bill.

A 50-50 tie. It’s happened before. The last time was in 2000, when Republican Vice President Dick Cheney acted as the tie-breaker until May 2001, when then-Sen. Jim Jeffords (R) of Vermont left the Republicans to become an independent and caucus with the Democrats.

In this case, Vice President Joe Biden would break ties for the Democrats. If he has designs on the presidency, though, that could impact his campaign, says Amy Black, a professor of political science at Wheaton College in Wheaton, Ill. Mr. Biden would have to adjust his schedule to stay within hailing distance of the Senate, since there is no electronic voting.

At the same time, the leader of the Senate Republicans, Mitch McConnell of Kentucky, and the Democrats’ leader, Senator Reid, would have to figure out how to structure the evenly-divided Senate. 

In 2000, it took months to settle on a way to organize committee membership. Given the short window of opportunity to “get things done” before the 2016 campaign season begins, such a time-crunch could be a real problem.

"We've had that situation before – 50-50 – and it's not fun,” said Don Stewart, spokesman for Senator McConnell, in an interview.

The Greg Orman factor.  Which party controls the Senate could come down to one man, the independent candidate from Kansas, businessman Greg Orman. He has not stated which caucus he will join if he wins. Democrats hope it will be with them; Republicans with them. Mr. Orman is looking for the best deal for Kansas.

But former Senate aide Mr. Manley says there’s not all that much that either leader can offer. Senator Reid was able to entice Jim Jeffords with a chairmanship. That won’t be the case for a freshman senator, though he’ll probably be able to get whatever committee assignments he wants.

“Some people think you can come in and swing for the fences. That’s not how it works,” Manley says.

Democrats hold the Senate. This looks like a long shot, given the direction of the polls, the president’s unpopularity, and the electoral map, which all favor Republicans. But if Democrats are successful in their get-out-the-vote efforts, it’s still possible.

Such an outcome would “shock” and “demoralize” Republicans, says Pitney. “I think in the minds of most Senate Republicans, they are already in the majority. They’ll think that something has been taken away from them. They'll think they have no chance for 2016.”

And that will become a self-fulfilling prophecy, according to Pitney. GOP senators will retire early. It will hurt fundraising.

In the end, “under no scenario are we going to have a very productive Congress,” Pitney concludes. “Really, the magic number is 60, and nobody’s going to have close to 60 votes. That’s going to make it tough to produce landmark legislation.”