Political calculations can change about as quickly as the news.

Just look at last week: The news that a speaker of the House announced his retirement, and a Robert Mueller Russia investigation that keeps ensnaring people close to the president, were drowned out temporarily when President Trump announced a military strike against Syria.

But barring deeper involvement in Syria, the midterm calculus remains the same — Democrats have a distinct advantage at this point.

That's true for several reasons — and it was highlighted by data from the Pew Research Center presented at a National Press Club panel last week for Washington embassy staffers from various countries (at which your author was a panelist).

The Pew presentation set the backdrop for the midterms well. It drew on interviews from multiple recent Pew surveys, and also looked at ones from 2017 with the same questions. In other words, it considered a lot of people's responses, much more than one typical poll.

There were some fascinating details about gender, race and education, differences between the generations, who's making up the parties and how that's changed over the last two decades. It was chock full of charts, which are used below (with permission) in this post.

Democrats have advantages — most principally an unpopular president

Trump's approval problems

Speaker Paul Ryan's retirement highlights the main question for the 2018 elections — which party will control the House? (The Senate is more of an uphill climb for Democrats, based on the multiple seats they are defending, so, for now, let's focus on the House).

Democrats have advantages in their quest to take back the House. First and foremost, the president's low approval ratings. It's been a chaotic start to the Trump presidency, and yet his approval ratings have remained steady, steadily low.

"There's been a lot more stability than change" on that measure, said Carroll Doherty, director of policy research for Pew. (Doherty presented the data.)

That's a major problem for the party in power. Almost more than anything else, presidential approval has tracked with the performance of the president's party in midterms.

History

Add that to the fact that history is not kind to a president's party in midterms, and it creates problems for GOP candidates.

For context of just how bad history is to the president's party in midterms, just three times in the last 84 years — 1934, 1998 and 2002 — has the president's party gained seats in the House.

And those were extraordinary years, as panelist Darrell West of the Brookings Institution pointed out:

  • In 1934, the country was dealing with the aftermath of the Great Depression;
  • In 1998, Republicans faced a backlash over their impeachment of President Clinton; and
  • 2002 was right after 9/11

On average, the president's party has lost 27 House seats in midterms since 1934 (25 in a president's first midterm).

And when the president's approval rating is below 50 percent, it's even worse. When that's the case, on average, the president's party loses 34 House seats, or 41 in his first midterm.

Enthusiasm

Republicans are also suffering from an enthusiasm gap. As Pew notes in the presentation slide below, more Democrats than Republicans are "looking forward" to the midterms, which is a notable shift from 2010 and 2014, two past midterm years when Republicans took over the House and Senate, respectively.

Look particularly at liberals versus conservatives. There's a 25-point gap between the two, with 83 percent of liberals looking forward to these midterms, as opposed to 58 percent of conservatives.

The percentage of people saying control of Congress is a factor in their vote is already higher now than it was in the last polls of the wave years of 2006, 2010 and 2014.

And Trump is a major factor — more so than Bush or Obama were in any of those three recent wave elections.

More Democratic voters say their vote this Fall is a vote against Trump than they said it was one against Bush in 2006 in the middle of the spiraling Iraq civil war.

Conversely, more Republican voters are saying their votes are a vote for Trump than they said their vote was one for Bush in 2006 — and it's also higher than the Democrats who said their vote was one for Obama in 2010, when Democrats lost 63 House seats.

Women

Driving much of that enthusiasm for Democrats are women.

A record number of women have signed up to be candidates. And the highest percentage of women in at least two decades are identifying as Democrats.

Congressional ballot

Democrats are consistently leading on the survey question of who Americans would prefer to have in charge of Congress, known to pollsters as the congressional ballot test.

All of the poll average aggregators show Democrats with a consistent advantage on this question this year. FiveThirtyEight has Democrats at +6.9 points, RealClearPolitics +6.6 and Huffington Post's Pollster also +6.6.

But before Democrats get too far ahead of themselves here and think they're a shoo-in, in 2006, Democrats had an 11.5-percentage-point advantage in the polls and finished with about an 8-point advantage in the actual results on election night nationally, according to the RealClearPolitics average that year.

And Democrats had a more even playing field. Republican gerrymandering has insulated many GOP congressional candidates from competitive races.

But there are signs that they're not all so confident.

Retirements

There are a record number of Republican retirements from the House this year — 39 are calling it quits from their congressional jobs.

The only year that comes close to this many retirements by either party were Democrats in 1992 when 41 of them exited. In 1992, Democrats only lost 10 seats, but it set up a very bad year for the party two years later in Bill Clinton's first midterm.

It's undoubtedly a bad sign for Republicans — and open seats are easier to win than defeating incumbents — but not always has the party with the most retirements seen the most losses.

Republican issue arguments haven't taken hold

Americans are saying they don't yet feel the benefits from the tax plan and have moved more in favor of free trade, which is counter to Trump's populist push.

On the tax plan, just by a 29-to-27 margin do Americans say it will have a mostly positive effect on them and their families in the years ahead. Even Republicans don't seem that confident in it. Just over half of them say it will have a positive effect.

Overall, the tax plan is not viewed positively for the country on the whole, with just 35 percent saying it will have a positive effect in the coming years; 40 percent say its effect will be mostly negative.

And on trade, something critical to President Trump's economic philosophy, Americans seem unconvinced.

A majority say free trade has been a good thing and more say it's likely helped their financial situation than hurt.

Republicans still retain some advantages

The economy

The economy continues to chug along. Unemployment is at its lowest in decades, and while GDP growth is slow, it continues to be positive.

And Pew finds that views of the economy are the highest they've been since the early aughts.

But some cold water on those views of the economy: They might not matter as much because of the partisan split.

Republicans are the ones now feeling good about the economy, flipping from when Obama was in office. Democrats, on the other hand, have also reversed themselves from the Obama years and now see it negatively.

Republicans' positive views of the economy might be pacifying for them. And anger — and being against someone or something — tend to be greater motivating factors in midterms (because it fires up activists).

That continues to be on Democrats' side.

Foreign policy

Trump continues to get negative marks overall and Americans are worried about the threat posed by North Korea.

But it could be worse.

The Syria strike was a reminder about the potential consequences of involvement in a foreign conflict. Americans are war-weary and especially wary of becoming entangled in another nation-building effort in a faraway land.

It's why the White House was so quick Sunday to respond when French President Emmanuel Macron said he had "convinced" Trump to "remain" in Syria after threatening to pull out a week and a half ago.

"The U.S. mission has not changed — the president has been clear that he wants U.S. forces to come home as quickly as possible," White House press secretary Sarah Sanders said. "We are determined to completely crush ISIS and create the conditions that will prevent its return. In addition, we expect our regional allies and partners to take greater responsibility both militarily and financially for securing the region."

Democrats are critical of Trump lacking a comprehensive approach in Syria, and Trump's foreign-policy doctrine is not at all clear — when should the U.S. intervene or not?

For Trump, he has struck Syria twice — both times limited and both times when pictures of the results of chemical weapons attacks became too difficult to ignore.

That means he understands the political risk of getting stuck in a place like Syria — even if it means not solving the problem long term. There is always the risk of escalation, and that could change the calculus — and quickly.

Gerrymandering

Republicans have a key structural advantage. After winning state legislatures and governors' races in 2010, they were able to draw maps to insulate their congressional candidates.

That was a task made easier by the fact that Democrats are so heavily clustered in cities. Because of that, Democratic votes are not being spread out.

In 2016, Republicans won 49.1 percent of the vote in House contests nationwide, according to the Cook Political Report, but 55 percent of seats. Democrats, on the other hand, won 48 percent of House votes and just 45 percent of seats.

Demography

Longer-term demographic trends continue to favor Democrats, as Pew's slides show.

But older voters are still in the GOP's corner — and they vote at higher rates.

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