With Republicans set to take control of the Senate in the wake of Tuesday’s midterm elections, TransCanada Corp’s (TSX: TRP, NYSE: TRP) long-stalled Keystone XL pipeline project could finally be near approval.

Prior to the midterms, Senate Republicans had previously tallied as many as 57 votes in favor of the pipeline, which given their minority status in the chamber meant that Keystone already boasts considerable bipartisan support.

But even that wasn’t enough to meet the filibuster-proof threshold of 60 votes.

Although the House Republican majority has voted repeatedly to approve the pipeline in recent years, the Senate Democratic majority hasn’t held a binding vote on it since 2012.

But with an expanded Republican majority in the House and as many as 54 Republican Senators in the next Congress (we’re still waiting for a final vote tally in Alaska, as well as a runoff election in Louisiana, though both outcomes appear favorable to the GOP), plus additional Democratic support, legislation approving the pipeline should now easily sail through both chambers early next year.

Indeed, Republicans have said approving Keystone XL is a top priority for the next Congress.

Nevertheless, it could still face President Obama’s veto. And even with bipartisan support, the new Republican majority in the Senate won’t have the 67 votes to override it.

So the question now is how Keystone will play into the president’s political calculus. As a lame duck with his final midterm now past, his political considerations will likely involve weighing the importance of key Democratic constituencies such as environmentalists and labor unions against the longer-term interests of a Democratic Party that once rode his coattails, but whose grasp on power has since substantially eroded.

Keystone XL, which has been sidelined by domestic U.S. politics since 2008, has long been controversial among environmentalists, who worry that the proposed 1,179-mile pipeline running from Alberta to Nebraska could pose a significant risk of spills, while also increasing greenhouse gas emissions (GHG).

The president has previously stated that he was unlikely to authorize a permit for the pipeline if it were to greatly increase emissions. The pipeline could carry as much as 830,000 barrels per day of mostly heavy, sour crude from Canada’s oil sands to U.S. refineries.

In addition to hoping to stymie emissions-intensive production from Canada’s oil sands by denying crude an easy path to market, environmentalists are also concerned about the emissions resulting from the difficult refining process, as well as crude’s eventual use as a fuel source.

However, when there’s demand for a commodity, it will find its way to market, as evidenced by producers resorting to shipping crude by rail, truck and even barge.

And if Canadian crude is going to get to market anyway, then from an environmental standpoint it all boils down to which mode of transportation is cleanest in terms of emissions. In fact, a U.S. State Department environmental assessment concluded that the Keystone XL pipeline was the most environmentally friendly means of transportation when compared to the aforementioned alternatives now in use.

But even if environmentalists are only a small constituency when it comes to the polls, they are becoming an increasingly important constituency when it comes to political fundraising.

Indeed, anti-Keystone billionaire Tom Steyer deployed $57 million via his NextGen Climate Action super PAC (political action committee) to help protect Democratic seats in the recent election. Altogether, environmentalist groups may have spent as much as $85 million on the midterms.

Then there are the labor unions, another core Democratic constituency, which are largely in favor of Keystone because they hope it will create new jobs. Although union membership has long been in decline, unions still represent about 11% of the U.S. workforce, so they are a significant source of votes, manpower for electioneering, and fundraising.

According to the Center for Responsive Politics, labor unions’ political spending accounted for 17%, or $89.5 million, of all outside spending by political interest groups during the recent election cycle.

If Obama ultimately decides it’s in his best interest to simply move forward with approving the pipeline, then he could pull a political jujitsu move on Republicans by proceeding with approving its permit before Congress can act.

Warren Mabee, director of the Institute for Energy and Environment Policy at Queen’s University, told the Toronto Star that while he doesn’t discount the possibility that Obama will veto any Keystone bill that crosses his desk, there’s a chance that he may bring the project forward for approval before legislation is introduced.

“He could just approve it now and take the wind out of the Republicans’ sails,” Mabee said. “If he waits for them to pass, then he suddenly looks weaker.”

During a visit to Canada in late October, U.S. Secretary of State John Kerry told a joint news conference held with Canadian Foreign Minister John Baird that he would certainly like to make a final decision on Keystone “sooner rather than later,” but that he couldn’t give a precise date.

Perhaps the Obama administration was simply waiting for the outcome of the midterms to see whether it would truly be cornered on Keystone.

Kerry’s comment suggests the administration may have been weighing the most opportune time to act.

If it acted before the elections, then it would have certainly alienated environmentalists. But now that the administration has been cornered, the most politically expedient thing for Obama to do may be to approve Keystone XL rather than veto it, as many expect.

That way, he’ll avoid the political showdown that could occur if Republicans subsequently tack on the approval to a must-pass spending bill.

And such a move could also help more moderate Democrats win back seats from Republicans in the next election by appealing to an electorate that’s clearly more concerned about the economy than environmental issues.