If anything is a lead-pipe cinch in American politics, it's that the party out of power in Washington, DC always cleans up in the midterm elections—particularly the first midterm. If you Google "midterm" and "Democrats" right now, you'll be bombarded with the phrases #BlueWave, "Blue Tsunami" and "That blue supervillain guy from the new Avengers movie."

With Trump's weak approval ratings and the history of off-year partisan backlash, "Speaker Nancy Pelosi" is a done deal. Except, in the era of Trump, there apparently are no "done deals." (Just ask his former contractors.)

"If the election were held today, I'm not sure who would win the House. First time I've been able to say that since summer of last year." That tweet from RealClearPolitics numbers-cruncher Sean Trende earlier this week stunned many on the Right. Trende, like the vast majority of poll-obsessed politicos, has been writing off the GOP House majority as a political "Dead Man Walking" for months.

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Not anymore.

And he's not alone. Amy Walter, national editor at Cook Political Report, agreed: "Same. Trump has had good month. Job approve slowly ticking up. Most important: Rs not fighting w/ each other, and Trump not attacking GOP leaders."

Same. Trump has had good month. Job approve slowly ticking up. Most important: Rs not fighting w/ each other, and Trump not attacking GOP leaders. https://t.co/JajyKUIZHY — amy walter (@amyewalter) May 15, 2018

Now Republicans are starting to allow themselves to dream: Is it even possible the GOP could hold onto the House in November?

Some of this is inspired by the surprising and steady rise of President Trump's approval ratings. In mid-December he was underwater by 21 points—a disaster for him and his party. Since then he's gotten that margin down to single digits -- 43 approve, 52 disapprove in the latest RealClearPolitics average. For Donald Trump, that's practically unanimous consent.

But to paraphrase scripture, "The Trump Giveth, the Trump Taketh Away." Every Republican knows this president is one bad morning on Twitter or one bad meeting with Bob Mueller away from blowing up his own success. Which is why the other numbers making news this week are so interesting.

On Wednesday a new Morning Consult/Politico poll hit. The takeaway headlines were about America's warmth toward North Korea and coolness to the idea of a Trump Nobel Prize, but buried in the crosstabs, there was something else.

When asked if an endorsement from Nancy Pelosi would make you more or less likely to support a candidate, 49 percent of self-identified Hillary Clinton supporters said "less." This is a problem because Pelosi and the Democrats' congressional leadership have been trying to craft tickets for November that they believe have a better chance of winning independent and cross-over Republican votes.

Democratic primary voters don't appear to be in the mood to listen. On Tuesday night, two progressive Democrats beat establishment-backed choices in swing house districts. Kara Eastman, a progressive activist who ran on a Bernie Sanders-style platform, beat former congressman and moderate Democrat Brad Ashford in Nebraska. In a swing open-seat district in Pennsylvania's Lehigh Valley, progressive attorney Susan Wild beat the better-known—and more moderate—District Attorney John Morganelli.

Democratic leaders seemed to have sensed earlier on that the November election would be more competitive than once thought. They've been working to nominate candidates in the Conor Lamb model—not as liberal as the Pelosi leadership, but more electable in their district.

Progressives, however, have been energized by their anti-Trump animus and are pushing back. In Texas's Seventh District, for example, there is open warfare between the Democratic Congressional Campaign Committee (DCCC) and progressives at that primary goes to a runoff on May 22nd. The DCCC took the unusual step of attacking a Democrat, Laura Moser, in hopes of keeping her off the ballot in favor of a more moderate candidate.

It didn't work, and now Moser has a very good chance of being the nominee in what is regarded as a rare, winnable GOP-held seat in Texas.

Echoes of Hillary vs. Bernie don't help Democrats focus on November. And party unity wasn't improved when last month, an audio tape was released of a private conversation between Democratic House Whip Steny Hoyer and progressive Democrat Levi Tillemann. Hoyer is heard asking the liberal to drop out of Colorado's 6th congressional district primary, and states that the party has already decided to back a more moderate candidate, Jason Crow.

If this sounds similar to the battle between Tea Party conservatives and the GOP establishment—it is. One reason Trump's numbers have steadily the past few months is because Republican voters are coalescing around him. There's more unity in the party over all. Some media reports say Majority Leader Sen. Mitch McConnell has explicitly asked President Trump to stop criticizing the GOP Senate. And in West Virginia, Trump went out of his way to clearly denounce Don "Trumpier than Trump" Blankenship—a very different performance from the mixed signals he sent regarding Judge Roy Moore in Alabama.

If Democrats are divided and Republicans are united, the GOP's chances of denying the Democrats the 23 seats they need goes up. But the real difference maker is Donald Trump.

"This is all about the President's performance," Trende says. "The economy is doing great, he's made big moves on North Korea and Israel that make him look presidential, and he's proven that—even when he's saying unpresidential things—he's not going to get us into a war or blow the world up."

"People were really worried about that when he told office," Trende says. "It's easy to dismiss, but it's true."

Morning Consult's Jeff Cartwright agrees that, if the GOP really is back in the game for the midterms (he says that's a big "if"), it's all Trump's doing.

"You can connect all the trends to Trump's approval numbers," Cartwright says. "At their worst, Trump was in the mid-30s and the Democrats had a double-digit lead in the generic ballot. Trump's turned that number around and that big generic-ballot margin is gone."

Cartwright also notes that Democratic hopes for that #BigWave don't have as much data behind them as some believe.

"When you look race by race in the special elections since 2016, you tend to see Democratic upsets, yes. But not blowouts. These have mostly been tight races."