WASHINGTON (MarketWatch)—With less than two months remaining before the midterm elections, there’s suddenly the possibility of a November surprise: that Democrats could retain control of the Senate. Recent forecasts show Democrats drawing almost even, or better, though others have Republicans gaining more than enough seats to retake the chamber.

That surprise would be a shock—albeit one that would soon give way to a familiar scenario, say analysts: more Washington gridlock.

“The markets had expected a big GOP win this fall, with Republicans easily capturing the Senate,” Greg Valliere of Potomac Research Group told MarketWatch in an email. “That suddenly looks less likely—and that could be a negative for investors who were anticipating things like the approval of the Keystone pipeline or tax reform next year.”

Democrats winning the Senate would keep Washington divided, since Republicans are expected to keep the House of Representatives. And that’s a recipe for getting little done.

Even if Democrats are able to fend off the GOP and keep control, they are likely to lose at least some seats—such as in Montana and South Dakota—that will make securing the 60 votes needed for major legislation even harder. The Republicans need to pick up six seats to take over the chamber. Democrats control the Senate 55-45.

A weakened Democratic majority would likely slow the Senate down even more. “It probably means another two years without a budget resolution or any fiscal deal,” said Stan Collender, a budget expert at Qorvis MSLGroup.

That doesn’t mean the Democrats won’t stick to their current playbook. Collender believes even if Democrats marginally control the Senate, they would push anew for higher revenues, much like they have tried to do this year—and failed. The party hasn’t been able to push through items like Sen. Elizabeth Warren’s student-loan bill—financed with a “Buffett tax” on incomes of $1 million and above—or close corporate tax loopholes like oil-company subsidies.

So there’s plenty of unfinished business. Just Monday night, Republicans blocked Democrats’ paycheck fairness act. “Democrats will keep fighting for fairness and equal treatment for women across the country,” said Senate Majority Leader Harry Reid after the vote.

A senior Senate Democratic aide said if Democrats win the chamber they will continue to try to advance legislation including paycheck fairness, raising the minimum wage and college affordability.

Republicans have already begun to lay out their agenda in the event they win the Senate, focusing on goals including approving the Keystone XL pipeline and repealing Obamacare’s medical-device tax.

No matter who wins the Senate, Congress will need to deal with raising the government’s debt ceiling. The government will hit its borrowing limit in mid-March. A more-conservative group of Republican senators and House lawmakers could use the borrowing limit to make demands for spending cuts. But if Democrats stay in charge of the Senate, don’t expect them to start a confrontation, says analyst Ethan Siegal of the Washington Exchange.

“If the Democrats keep control of the Senate, they’re not going to go out of their way in 2015 to have a debt-ceiling fight,” says Siegal, whose firm provides research for institutional investors.

The place to watch on the debt ceiling will be the House, says Andy Friedman, who formerly ran the tax and corporate groups at law firm Covington & Burling in Washington. “There will be some new tea-partiers in the House, like the guy who knocked off Eric Cantor,” says Friedman, now principal at newsletter the Washington Update. Former House Majority Leader Cantor lost his primary in June to Dave Brat.

Friedman says he doesn’t think there will be a default. And he believes the markets generally have built in a stalemate in Congress, except for events like a debt-ceiling fight. “It could be touch and go for a while” if there’s another brawl over raising the borrowing limit, he says.

For right now, investors are focused elsewhere, says Sam Stovall, U.S. equity strategist at S&P Capital IQ.

“Quite frankly, I don’t think U.S. investors really care about the coming midterm elections,” he said in an email. “Most investors probably think that both the Democrats and Republicans should be renamed ‘The Do Nothings.’ I think investors’ focus is primarily on the Fed and secondarily split between the Scottish referendum and China’s growth prospects.”