As President Trump’s troubles mount, the long-standing expectation that Democrats will gain several House and Senate seats in 2018 has only intensified. At this point, many observers are expecting a bloodbath – and they’re right. But for structural, historical, and intangible reasons, expect the bloodbath to be for Democrats as the GOP further expands its dominance in both houses of Congress.

I see five reasons Democrats on Capitol Hill should stock up on life preservers.

1) Trump’s unpopularity won’t matter. Republicans and moderates who like Trump will vote Republican out sympathy with the president’s state of siege, but many of those who don’t like him will vote Republican as well. That’s because Americans tend to like “their guy” (or woman) in Washington whoever’s president and whatever the overall political climate.

The power of incumbency in Congress can’t be overstated – and of course it tends to favor the party already in power. In 2016, 97 percent of House members and 87 percent of Senators running for re-election won. Even in the “wave election” of 2014, the numbers were 95 percent and 82 percent, respectively.

The most effective way, then, for a party to take advantage of a national political mood and pick up seats is to run strong candidates to replace legislators who retire. That doesn’t seem a promising plan for Democrats in next year’s elections.

Right now, 2018 looks to be the first year in the history of Senate elections in which no incumbent retires. On average, seven Senate seats per cycle open up, and there have always been at least two.

Retirements in the House so far don’t look good for Democrats either. As of August 10, only 18 Representatives (out of 435) had announced they were retiring or running for another office, most are from safe seats – except for a Florida seat that might flip to the Democrats and seats in Minnesota and Nevada that might flip to the Republicans. The fact those numbers are so small is good news for the party in power, of course.

2) The Senate map is savage for Democrats. Only one Republican is up for re-election in a state that Hillary Clinton won last year, while 10 Democratic Senators are up for re-election in states that President Trump won last year. Many of those (North Dakota, Indiana, Montana, and West Virginia, to name a few) skew decidedly rightward. Of the Senate seats most likely to flip parties next year, only two (Nevada and Arizona) are currently held by Republicans.

Then there’s Sen. Robert Menendez (D-N.J.), who will be replaced by a Republican if convicted in his corruption trial next month and then expelled from the GOP-led Senate.

3) Structural reasons lock the Democrats out of the House. In fact, winning the House gets harder for Democrats every cycle. Gerrymandering has already created Republican-friendly maps throughout the country (an advantage that will likely grow in the next redistricting cycle given Republican dominance in the states). Further, the voter ID laws in 29 states tend to help Republicans, and in states like Missouri and Texas (both of which have Senate races next year), voter ID requirements have been getting stricter.

The obstacles preventing a Democratic wave election are just too steep. Earlier this month, FiveThirtyEight’s David Wasserman shocked the political world with this nugget of data: “Even if Democrats were to win every single 2018 House and Senate race for seats representing places that Hillary Clinton won or that Trump won by less than 3 percentage points — a pretty good midterm by historical standards — they could still fall short of the House majority and lose five Senate seats.”

America simply has fewer swing districts than it used to, because America has fewer swing voters. Blame social media, blame polarizing figures like Donald Trump, but the makeup of Congress can’t change dramatically in an environment with ossified voting patterns.

And Democrats don’t have much of a “bench,” either. The most successful Congressional candidates are often state legislators and statewide officeholders, but the number of Democratic elected officials in the 50 states shrank dramatically in the Obama years. You can’t defeat somebody with nobody.

4) Democrats have not learned the lessons of 2016. Democratic explanations for why they lost last year are completely out-of-touch, which means they can’t learn from their mistakes. Some Democrats think they lost because struggling white Americans were fooled into thinking Trump would help them, and so they’ll turn against the president when their economic situations don’t improve. That’s a sociology professor’s fantasy of American politics that completely misses the cultural factors for Trump’s win – and Hillary Clinton’s loss.

Alternatively, some Democrats think they lost because of “white resentment” – which isn’t far off, but not in the way they think. Trump voters weren’t mostly resentful of African-Americans and Latinos; they resented the racial politics of liberal whites, who disdained their lifestyles and portrayed their legitimate policy differences on issues like affirmative action and welfare as evidence of racial animus. Once Clinton was done describing half of Trump supporters as “deplorables” for their racial and other views, earning their votes was a near-impossible task.

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Other Democrats look at the enthusiasm for Bernie Sanders in the 2016 primaries and see his far-left “democratic socialism” as the ticket to changing the momentum of American politics. That view confuses excitement in a primary with potential in a general election. More Sanders-style Democrat candidates would be a delicious gift to the GOP.

There’s one other piece of evidence Democrats aren’t learning from 2016: Nancy Pelosi still runs their caucus in the House. Americans don’t like her, for good reasons (her extreme liberalism and her deceit on Obamacare) and bad (she’s a woman from San Francisco who was alive during the Roosevelt Administration). But until they find a young, telegenic, vibrant House member to serve as minority leader, Pelosi will be an albatross in race after race, the GOP delighting in connecting her to Democrat House candidates.

5) Most importantly, conventional wisdom has lost its wisdom. For the last year and a half, the experts have constantly told us that NOW American politics is reverting to normal. The point to faulty historical trends, flawed polls, and irrelevant electoral data – misreading the Zeitgeist and gaping bewildered at the Trump phenomenon. At this point when I hear an expert predict doom for the GOP I automatically presume the opposite will happen, since the last time they got it right, Trump was still hosting a reality show. Just you watch.

David Benkof is a columnist for The Daily Caller. Follow him on Twitter (@DavidBenkof) or Facebook, or E-mail him at DavidBenkof@gmail.com.