Trump gives his State of the Union address tonight. Here's what to watch for

U.S. President Donald Trump will deliver his State of the Union address Tuesday night, and it comes with his approval ratings sinking as the crucial midterm elections approach.

"It's going to be a long speech because we have so much to talk about," Trump said Monday at the White House.

The annual presidential address, to a joint session of Congress, is broadcast on all the main U.S. television networks and you can also watch it on the CBC News website or on CBC News Network starting at 9 p.m. ET.

Although total viewership has been dwindling since its peak in the 1990s, the address remains an important event on the political calendar watched by millions of Americans. Trump's first-term speeches drew on average more than 44 million viewers, according to Nielsen. Here are some key things to look for tonight:

By tradition, the justices of the U.S. Supreme Court get front-row-centre seats in the House for the State of the Union address, putting them in direct line of sight of the president.

Given how angrily Trump reacted to the court's decision last week to strike down the bulk of his global tariffs, it will be fascinating to see the dynamic.

During his White House news conference on Friday, Trump called the justices who ruled against him "fools and lapdogs." Will Trump be just as eager to insult them to their faces? Bring the popcorn.

Trump could also use the speech to lay out more of his plan to impose other tariffs in an attempt to replace those now declared illegal, which he had levied on Canada, Mexico and other countries around the world under the International Emergency Economic Powers Act.

If there was any doubt that Trump will boast about the economy, he wiped that away during Monday's event at the White House.

"We have the greatest economy we've ever had," he said. "I'm making a speech [Tuesday] night and you'll be hearing me say that."

Trump's senior staff have been trying for months to pivot the president toward emphasizing economic and cost-of-living messages in his public appearances. Their boss, however, tends to go off script, and has expressed frustration that Americans don't seem to feel the economy is as great as he says it is.

Jonathan Ladd, an associate professor in the McCourt School of Public Policy at Georgetown University, says Trump's ability to shift public opinion through the speech is limited.

"It's very hard to change the popularity of your party and your popularity as a president by a State of the Union message," Ladd told CBC News.

On average, recent polling suggests 41 per cent of U.S. voters approve of Trump's overall performance as president, and just 35 per cent approve of the job he's doing on inflation, according to Silver Bulletin, a poll-tracking and analysis newsletter.