(CNN) It's become a numbing Washington ritual. Donald Trump shatters a traditional boundary on the exercise of presidential power. Or he uses inflammatory language that stirs racial animosities. Or he's hit by new revelations in the overlapping investigations into his campaign's contacts with foreign governments in 2016 and his own tangled financial and personal affairs before the presidency.

As each of these bombshells detonate, sometimes within hours of each other, congressional Republican leaders then react with little more than a shrug. Even more important, the vast majority of the Republican electoral coalition increasingly responds the same way.

All of these dynamics played out multiple times this past week. Trump shattered boundaries by openly demanding the Department of Justice investigate the ongoing special counsel examination of his campaign and by privately pressuring the US Postal Service to raise rates on Amazon , whose owner, Jeff Bezos, also owns the Washington Post, which Trump considers an enemy. He used George Wallace-like language in describing members of the MS-13 gang as "animals." And he faced the startling revelation that during the 2016 campaign his son Donald Trump Jr., who had earlier convened with Russians offering damaging information on Hillary Clinton, also met with emissaries of Middle Eastern governments offering to help in the election.

After all that, Republicans responded this week with the sort of silence usually expected from the crowd at the 18th hole of a golf tournament.

The Trump paradox

The elimination of any distance between Trump and the conventional Republican interests that controlled the party before him has happened so incrementally it can be difficult to discern from day to day. But it remains one of the central political dynamics of 2018. Over the long term, Trump's success at stamping his polarizing brand on the GOP remains a huge electoral gamble for the party because it risks alienating the young, well-educated and diverse groups growing, rather than shrinking, in the electorate.

But in the near-term, the GOP's choice to ally so unequivocally with such a unique president may have the paradoxical effect of producing a much more conventional midterm election than seemed possible earlier this year. And that means for Democrats to secure the gains they seek in November, they will need to overcome the typical challenges they face in a midterm election far more than they expected even only a few months ago.

In both 2010 and 2014, the two midterm elections under Barack Obama, Democrats suffered huge losses. Each time the party faced similar problems. The biggest was a collapse in turnout among young voters, and a smaller, but still significant, decline among minorities. In both 2010 and 2014, the share of the vote cast by young adults 18-29, a strongly Democratic-leaning group, was fully six percentage points lower than in the presidential race just two years earlier, according to exit polls.

Each time, the non-white share of the vote dropped three points compared to the previous presidential contest. In turn, seniors, who now lean strongly toward the GOP, represented a significantly greater share of the vote in each midterm than in the previous presidential race.

Those turnout problems for Democrats were compounded by anemic performances among white men and women without a college degree, and white men with degrees. In both 2010 and 2014, according to exit polls, Democratic congressional candidates carried no more than 36% of voters in each of those groups. The party's performance among college-educated white women was better (43% in 2010 and 47% in 2014) but still below their strongest showings with those women in recent years.

Through much of 2017, it appeared possible that Trump's general weakness might solve all of these traditional Democratic problems -- or at least render them inconsequential.

Especially during the extended Republican struggle to repeal the Affordable Care Act, Trump's presidency sometimes seemed at risk of functional collapse under the combined pressure of special counsel Robert Mueller's Russian election meddling investigation, internal administrative chaos and incompetence, chronic divisions between the White House and congressional Republicans and the president's inability or unwillingness to control a belligerent and volatile temperament.

It's still possible any of those factors -- or some combination of them -- could politically debilitate Trump or, much less likely, even force him for office. But it no longer seems plausible that he will simply implode.

Rather over the past several months -- particularly since the passage of the GOP tax plan late last year -- Trump has shown clear signs of consolidating more of the usual Republican institutional and electoral base than he had earlier, despite all the norm-breaking excesses of his presidency. His approval rating in most polls has moved up from the high thirties to the low forties. That's still weaker than it should be given the robust economy, but a clear sign that he has recaptured many traditionally center-right voters. Over that same period, the tightening generic ballot test measuring preferences for the 2018 election show much of that same support drifting back, like metal filings toward a magnet, around congressional Republicans.

That doesn't mean Democrats can't retake the House or conceivably even the Senate in 2018 or beat Trump in 2020. But it does mean they can't rely on Republican disarray to power those victories. Despite all of Trump's unique liabilities, the key institutions and voter blocks of red America show every sign of mobilizing to maintain their control of power in Washington.

Support for Trump in key groups

Since he took office, Trump's approval rating has always been high among self-identified Republicans and core Republican groups. The most recent national polls from CNN and the Pew Research Center , for instance, both put his approval rating among white men without a college degree at a robust 66%. More than three-fifths of those men also said they intend to support Republican candidates for Congress this fall.

Even more telling may be the preferences the polls recorded among two groups of generally Republican-leaning white voters who Democrats have hoped would abandon the GOP under Trump: white men with a college degree, and white women without one. The two polls vary slightly in their measurement of how those voters view Trump himself: in the CNN poll, both groups give him an approval rating around 50%, while in the Pew Survey, he draws about 45% approval from both.

Yet both surveys show that Republicans now hold a solid lead with both groups in their preferences for the midterm election. Both surveys show Republicans now drawing over 50% of college-educated white men, while among blue-collar women Pew puts the GOP slightly above 50% and CNN shows them just slightly below. In each survey, Democrats are winning only about two-fifths of both groups. Those advantages aren't as lopsided as Republicans enjoyed in 2010 or 2014, but if they endure, they may be sufficient to blunt the Democrats' gains in 2018.

A shift to Democrats by college-educated women

The clearest improvement for Democrats from 2010 and 2014 is that both polls show Trump facing disapproval from about two-thirds of college-educated white women. Almost exactly three-fifths of those women in each survey say they plan to vote Democratic in November. That's significantly more than Democrats have won among that group in any congressional election since 1992, according to exit polls, and that shift alone could allow them to capture several seats Republicans hold in white-collar suburbs. The 2017 elections also have demonstrated a high level of engagement among African-American voters, especially women-and they register passionate distaste for Trump in polls.

But if those are the only ways the electorate in 2018 differs from 2010 and 2014, Democrats would likely be disappointed in the results. The party is betting on greater engagement from its core voters than among Republicans, but a succession of Trump policy decisions aimed at energizing the GOP base (such as hardline approaches to immigration) may be narrowing that gap: the CNN survey showed only a modest six percentage point gap between the share of Republican and Democratic-leaning voters who said they were very enthusiastic about voting.

And while recent reports show voter registration rising among younger voters in some key states, the proportion of younger adults who say they are closely following news about the election was far lower than for any other age group in the Pew poll. That's despite the deep opposition to Trump that they register in all surveys.

The headwinds facing Republicans in November remain formidable: the last three times one party went into a midterm election with unified control of government (the Democrats in 1994 and 2010 and the Republicans in 2006) voters revoked it. Trump's approval rating after his recent gains is higher than George W. Bush's was at the time of the 2006 Republican loss, but still lower than Obama or Bill Clinton during their midterm defeats. And while polls show mixed evidence of a Democratic turnout advantage in November, in practice, party voters have stampeded to the polls in the actual elections held since Trump took office. Fundraising for Democrats is astronomical as well.

But compared to six months ago, the constant gales swirling around Trump no longer look as certain to blow away all of the GOP's traditional midterm advantages. Nor does it appear likely that any new revelation in the various investigations of Trump will dissolve support for him or the GOP Congress. As in earlier midterm elections, mobilizing young people still looks like a challenge for Democrats, as does persuading more blue-collar white women and white-collar white men.

In other words, even with all of the turmoil around Trump, there is no cavalry coming to rescue blue America from Republican dominance of Washington. Democrats will need to storm those gates themselves, beginning with finding ways to overcome the resurfacing obstacles that have hurt them so badly in midterm elections before.