Washington (CNN) 2017 is almost in the books — and so are another 12 months of public opinion polling.

The calendar year that President Donald Trump spent settling into the White House has been marked by consistently low ratings from a majority of the American public.

But this year also has seen new highs for the economy, growing popularity for Obamacare and widening public opinion gaps ahead of the 2018 midterm elections next year.

Here are the seven most important polling trends from 2017:

1. Trump's job approval hits record-breaking lows

Trump will finish his first calendar year in office with just a 35% approval rating — the lowest at this point in a new president's term stretching back to the Eisenhower administration, according to polling by CNN, CNN/ORC, CNN/USA Today/Gallup and Gallup.

But it's not only low for the beginning of a new term. Trump's quarterly approval numbers are some of the lowest since Gallup began tracking them for presidents — falling in the 11th percentile of out of 288 presidential quarters tracked by Gallup over the last half century.

Trump tweeted Friday morning that his approval numbers are similar to Obama's numbers at the one-year mark, but every reputable pollster shows otherwise

2. GOP share of the electorate shrinks to new low

The number of Republicans in the American electorate has shrunk to its lowest in a quarter century after Trump's election last year, according to numbers from Gallup.

Only 38% of Americans self-identify as Republicans or Republican-leaning independents during 2017, while 45% of Americans say they are Democrats or Democratic-leaning independents.

That also means roughly one in eight people who identified as Republicans or Republican-leaning in November 2016 no longer do so. (The number of Democrats has held roughly steady over the same period.)

3. Economy soars to new heights — and Trump gets some credit

Some good news on the economy: A broad 68% of Americans now say the US economy is in good shape, the most since before the September 11, 2001, terrorist attacks.

Still, the gap between the opinion on the strong economy and Trump's low approval rating -- 33 points -- is the largest negative split in more than two decades of polls from CNN and Gallup.

But it's worth noting Trump is starting to get more credit for the booming economy almost a full year into his time in the White House. A full two-thirds of Americans said former President Barack Obama was primarily responsible for the state of the economy in March — but Americans are roughly evenly divided a year after Trump's election.

4. Congressional ballot trend signals Democratic landslide in 2018 midterms

A broad 56% of registered voters say they plan to vote for a Democrat in next year's midterm elections while only 38% say they plan to vote for a Republican — the widest gap at this point in a midterm cycle dating back to at least 1997.

A president's party typically loses seats in midterm elections, but Republicans may be poised for dramatic losses in 2018.

5. Did Obamacare's popularity sink GOP repeal?

Obamacare hasn't had a net negative favorability rating at all this year, according to polling from the Kaiser Family Foundation , a stark change from its stretch of negative ratings early in 2016 and most of the prior five years.

The most recent numbers show the sweeping 2010 health care law with a 50% favorable and 46% unfavorable rating, though the positive gap has climbed as high as 13 points in August.

This positive trend is one major reason why Republicans struggled — and ultimately failed — to pass a repeal-and-replace plan through the Senate over the last year.

6. Russia investigation still looms large into 2018

A majority of Americans say they believe Trump has made false statements about Russia, and 61% called the investigation into the country's interference in the 2016 race a serious matter in recent CNN polling

This number has held steady over the last year, showing that the importance of the probe isn't fading with time more than after the election. Still, it's worth noting only 16% of Republicans see the Russian interference as a serious matter worthy of investigation — the lowest figure yet in CNN polling.

7. US global reputation takes a hit under Trump

Perceptions about the United States and the President took a major hit on the world stage in 2017, according to numbers from the Pew Research Center . (Pew conducted surveys in 37 countries during the spring and reported global medians in June.) Check out this chart from Pew:

A whopping 74% of those living in other countries say they have no confidence in Trump, a stark change from when only 23% said they had no confidence in Obama.

The number with a favorable view of the country overall also shrank from 64% under Obama to just 49% under Trump, though it's still a net positive.