All of the votes haven’t even been counted in the 2016 elections, but it’s not too early to look ahead to 2018.

Even before Nov. 8, there was plenty of discussion (and even an expectation) that Republicans would bounce back from this year’s election losses due to a favorable Senate map in 2018, particularly with Hillary Clinton in the White House.

But Republicans held serve this year (only losing two seats and retaining control of the chamber), and now have an opportunity to turn that favorable map into a filibuster-proof majority. In two years, 10 Democratic senators will be up for re-election in states won by Donald Trump this year.

In some cases, the discrepancy is dramatic.

In 2012, Democratic Sen. Joe Manchin III won his Senate race in West Virginia with 61 percent of the vote, while Trump carried the state this year with 69 percent.

That dynamic will have an immediate impact on Manchin and other vulnerable Democrats who will feel cross-pressured next Congress by party leadership, telling them to block President Trump at every opportunity, and their constituents, who just voted to put the political outsider in the Oval Office.

But Trump’s presidential victory complicates Republicans’ opportunity to gain Senate seats in 2018. The president’s party often suffers in midterm elections, as Roll Call’s Alex Roarty pointed out in his recent story. 

Not only are Democrats defending more seats in 2018 (25, including two held by independents who caucus with the Democrats), compared to just eight by the Republicans, but 17 of those Democrats were initially elected in 2006 or 2012, which were good or great Democratic years. Only time will tell what kind of political environment 2018 turns out to be. And retirements and primaries will help shape the battleground as well.

But even with Trump in the White House, Democrats should be concerned. This was the first year, over the course of a century since senators have been directly elected, that the presidential outcome matched the outcome of the Senate race in each state, according to number-crunching by FiveThirtyEight. 

If the 2018 states follow the 2016 presidential outcome in their votes for the Senate, Republicans will gain nine Senate seats and have a filibuster-proof majority.