Eight months into the 2018 election cycle and with 16 months to go, the fundamentals of the Senate map haven’t changed.

One state has been added to the map: Alabama.

When Republican Sen. Jeff Sessions joined President Donald Trump’s Cabinet as attorney general, then-Gov. Robert Bentley appointed Luther Strange to replace him. But Kay Ivey, the new governor, set a special election to fill the remainder of Sessions’ term for this year rather than waiting for the next regularly scheduled election in 2018. Strange must now navigate a competitive GOP primary next month.

Democrats are still on the defensive this cycle. They’ve got 25 senators up for re-election, including 10 in states President Donald Trump won in 2016. Five of those states voted for both Trump and Mitt Romney in the last two presidential elections. By comparison, there are just eight Republican senators up for re-election, with only one (Dean Heller in Nevada) running in a state Hillary Clinton won in November.

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In the short term, those Trump-state Democrats were supposed to be a reservoir of votes for Senate Republicans and the White House. But it just hasn’t worked out that way on most issues.

Three Trump-state Democrats — Heidi Heitkamp of North Dakota, Joe Manchin III of West Virginia, and Joe Donnelly of Indiana — voted to confirm Neil Gorsuch to the Supreme Court. But otherwise, there isn’t a lot of evidence that the most vulnerable Democratic senators are worried about opposing the president.

Those Trump-state Democrats were supposed to translate into a large batch of takeover opportunities next year. But Republicans can’t get too cocky about the map.

Since 1982, a total of 110 out of 114 senators from the opposite party of the president have won re-election in midterms, according to Harry Enten at FiveThirtyEight. Of course that rate of 96 percent is partially dependent on the map of each cycle, but that’s not a small sample size and Democrats have some savvy incumbents up this cycle.

So while Republicans should expand their majority significantly, according to the presidential map, midterm election realities and the strength of the Democratic incumbents could make that task more difficult.

History isn’t as kind to senators from the same party as the president who are up for re-election in midterms. Their re-election rate is 80 percent (103 out of 128) since 1982. That’s bad news for the GOP’s Heller and Jeff Flake of Arizona.

Re-electing Heller and Flake should be a priority for Republicans because it will help the party gain seats. But Trump and his allies are more concerned with passing his legislative agenda now, and have threatened to run attack ads against certain Republican senators whom they view as obstacles.

While they might disagree on the tactics, GOP strategists agree that Republicans need to deliver on more legislative promises to avoid voter apathy next year. If Trump supporters blame congressional Republicans for blocking the president’s agenda, and don’t turn out to vote, it could cause a GOP catastrophe.

Even though a Democratic majority is unlikely (despite them only needing to gain three seats), it also shouldn’t be dismissed. Republicans faced a difficult map and a historically unpopular presidential nominee in 2016, yet the party limited its losses and held the majority.