LIVE: See the House and Senate results of the highly anticipated 2018 midterm elections as they come in

Samantha Lee/Business Insider; Stefan Zaklin/Getty Images

• The 2018 midterm elections will determine whether Democrats or Republicans control Congress.
• Though liberal voters across the country are fired up after the first two years of Republican control, it's far from guaranteed that they'll turn up in great enough numbers to deliver the House and Senate back to Democrats.
• President Donald Trump and his allies have been whipping up conservative voters in recent days, campaigning on the threat of a migrant caravan making its way to the United States, and boasting of the roaring economy.
• See the results below for all of the House and Senate races in this interactive graphic, which we'll be updating live throughout the night as they come in.

Americans hit the polls on Tuesday to vote in midterm elections that have evolved into a referendum on President Donald Trump, and the party that has spent much of the last two years defending him.

The tumultuous first 21 months of the Trump presidency has fired up progressives across the country, and prompted a swell of left-wing activism on policies like healthcare, gun control, and immigration - and a bitter crusade against broader societal issues ranging from sexual misconduct to rising white nationalism.

LIVE UPDATES: Follow our live coverage of the 2018 midterm elections here.

But it remains to be seen whether Democrats' rage will amount to the so-called "blue wave" they've anticipated for nearly two years, or whether it's even enough to gain the 23 seats needed to eke out a Democratic majority in the House.

Trump and his allies have been working to whip up conservative voters into a furor ahead of the midterms. A slow-moving caravan of thousands of Central American migrants trekking to the US has served as ready fodder for Trump's diatribes for border security and immigration reform, and a roaring economy has helped the GOP foster confidence in their leadership.

But nonetheless, Republicans have been bracing for a loss in the House, though they anticipate keeping ahold of the Senate. Trump has also sought to temper expectations in recent days that Republicans would hold the House, saying he was more focused on campaigning for Senate races.

A major surge in early voting also sparked speculation that the so-called "Trump effect" was motivating progressive voters to turn out in record numbers - but as numerous election experts have pointed out, early voting has been a rising trend for years, and it's unclear whether all those early voters support Republicans or Democrats.

Here's a look at all of the contested Senate and House races, and how the two parties are faring:

The prediction numbers are from Real Clear Politics and the result numbers are from Decision Desk.

Samantha Lee contributed.