We know what to expect from midterm elections in a president's first term. History tells us that the party holding the White House generally loses seats in Congress. When presidents have approval ratings below 50 percent, they lose even more seats — and President Trump has never been close to sniffing 50 percent. It's little surprise, then, that Democrats confidently expect to pick up loads of seats in November's election, perhaps enough to wrest back control of the House, if not the Senate.

This may well be folly.

Democrats were cocky in 2016, too, assuming that their usual grip on the "blue wall" of Midwestern states was nearly inviolable. Voters surprised Democrats, and they may still have a surprise or two left in store for 2018 if Democrats fail to learn why their national fortunes sank to their lowest ebb since the Calvin Coolidge era.

There's no denying that history paints a bleak picture for Trump and Republicans. Since Franklin Roosevelt won nine seats in the 1934 midterms, only one president has managed to hold serve the first time out: George W. Bush. The 2002 midterms added eight seats to the GOP's House majority and gave them back control of the Senate with a pickup of two seats. This victory was attributable in large part to the national mood after the 9/11 attacks.

Otherwise, the electoral track record in a president's first midterm is uniformly bad, and sometimes disastrous. Barack Obama and Bill Clinton lost first-midterm landslides that shifted control of Congress (63 and 52 House seats, respectively), and even the relatively popular Ronald Reagan lost 26 seats in 1982. Harry Truman lost 45 seats in 1946 despite having won World War II just the year before.

History isn't the only headwind for Trump and Republicans. Almost three dozen GOP retirements in the House have opened up more opportunities for Democrats. Most of the districts are solidly Republican, but a few — such as the seats held by retiring Ed Royce and Darrell Issa in California — were expected to be competitive. And recent results in special elections suggest that Republicans might be losing some of their advantage in states Trump won in 2016. A loss in a Wisconsin state Senate election on Tuesday prompted GOP Gov. Scott Walker to issue "a wake-up call for Republicans" in the GOP-controlled state. Former Wisconsin radio host Charlie Sykes was told by a "prominent WI Republican" that the party is "losing independent and educated women in droves." It's the 34th state legislative seat lost by Republicans over the past year (although that's only a small dent in the nearly 1,000 state legislative seats the GOP won from Democrats over the preceding eight years).

Clearly, the smart money is on Democrats in 2018. These portents, combined with Trump's stubbornly low approval numbers, suggest that a blue wave is coming in November.

And yet ...

The year is young, and there are reasons to doubt whether Democrats will significantly expand their footprint from the previous four congressional cycles in which Republicans have held the majority, even while Barack Obama won re-election. The biggest wild card is the one Republicans just played — their tax reform bill — and the Democrats' continuing attempt to describe it as a disaster for taxpayers.

Democratic hyperbole prior to the late December vote had a significant impact on the bill. Somewhat remarkably for a tax cut, the bill only garnered 37 percent support, thanks in large part to doomsday descriptions by opponents who claimed that the bill's repeal of the ObamaCare mandate that every American obtain health insurance would result in people dying — literally. Democrats in Congress routinely mischaracterized the cuts by claiming that working- and middle-class Americans would see no benefits at all, and that companies would hoard the excess profits rather than passing along benefits to workers or consumers.

After the bill passed, companies with millions of workers began raising wages (oft-reviled retailers Walmart and Target among them), paying bonuses, and announcing infrastructure investments expected to fuel job creation. Apple — hardly a harbinger of Trumpist conservo-populist ideals — announced on Wednesday that it would pump $350 billion into its U.S. operations over the next five years, thanks in large part to the tax bill's opening for repatriating its capital from overseas.

Rather than adjusting to the reality of these tax cuts, Democrats have tried telling taxpayers that they can't believe their own eyes — or bank accounts — when it comes to finding benefit in these developments. House Minority Leader Nancy Pelosi called an additional $2,000 in bonuses "pathetic … crumbs" last week, a little over six years after calling a $40 uptick every two weeks from the 2011 budget compromise "a victory for the American people." For those who see $2,000 as a windfall, the "crumbs" remark sounds awful, a form of snobbery that will only play well among the Beltway elite.

Bear in mind that in most cases, American workers have yet to see any impact from tax reform. The bonuses are in the near future, as are the implementations of new withholding tables at most U.S. employers. And yet a new Survey Monkey poll shows a significant improvement in polling for the tax reform bill, rising from 37 percent approval in that series in mid-December to 46 percent this week. Overall consumer confidence "rose significantly in January after remaining flat for most of 2017," The New York Times reports.

Imagine what will happen when the impact of the tax cuts actually hits American paychecks. The cognitive dissonance between Democratic hyperbole and personal voter experience will be massive. And in a country where "it's the economy, stupid" still acts as one of the best predictive models for voter behavior, that dissonance will get felt in the same places where Democrats have been on the retreat: the middle-class, middle-America districts that have gone red for nearly a decade at all levels of electoral politics. That would leave Democrats with the same coastal-urban enclave footprint they have now.

A blue wave may still be coming. But the tax reform bill and its impact on the economy have not yet been calculated into those odds, and the exposure of Democratic hyperbole and snobbery has not yet been fully played out either. Hold off on any bets for now. So often, pride goes before the fall. And Democrats today are nothing if not prideful about their 2018 prospects.