Here is Bernie Sanders, looking to become president in the year he turns a tender 80, bringing forward a medicare-for-everyone plank like in Canada. He gets his fellow Democrats all excited about it. The party's stars sign up for the socialist turn.

And here's kingmaker Steve Bannon, out of the White House but in a 60 Minutes interview looking every bit as influential as when he was in it. He's now styling himself as "the streetfighter," the term often used to describe Canada's Jean Chrétien back in the days when the Liberals, as nativist Mr. Bannon does today, touted economic nationalism.

It was thought that Mr. Sanders was boneyard-bound politically after his primaries' insurgency was snuffed out by Hillary Clinton. It was thought Mr. Bannon's banishment from Donald Trump's inner sanctum might spell the end of his remarkable Svengali-like turn on the Republican stage.

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But the two men are still defining or, if you will, redefining U.S. politics. As in: far right, far left, goodbye middle.

Mr. Bannon cut quite the figure in his rock 'em, sock 'em 60 Minutes interview. Wearing not one but two button-down shirts and looking as if he hadn't had a bath since July, he vowed to be Mr. Trump's wingman or, more accurately, bomb thrower. The target, weirdly enough, isn't the Democrats so much as his own party.

Mr. Bannon, who views most traditional Republicans with "contempt, total and complete contempt," vowed to fight in nomination battles to take down entrenched party members who don't adhere to Mr. Trump's wall-building nationalist, populist pitch.

Democrats could only grin. Mr. Trump meanwhile continues his dalliances with the opposition party. Last week, he reached an agreement with the Democrats on the debt ceiling. This week, they flirt on a deal for extended protections for young undocumented immigrants.

By training their sights on their own Republican flock, Mr. Trump and Mr. Bannon could shatter the party enough to help the Democrats roar back to power. The Trump/Bannon nativist preachings – that the country went to hell in a hand basket because of such things as rotten trade agreements – increasingly has the look of sophistry.

The argument is that the low 4.4-per-cent unemployment rate doesn't reflect the misery of a citizenry who haven't shared in the economic upturn of recent years. But a U.S. Census Bureau report this week said in fact the recovery was distributing benefits more broadly, that the median household income jumped 3.2 per cent after inflation last year, that poverty numbers are declining. Meanwhile, interest rates are low, inflation is low and the stock market is high.

Mr. Trump and Mr. Bannon are trapped. They have to adhere to the tenets of an election-campaign platform built on bilge. Otherwise they'll be seen as promise breakers.

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But if they are doing Democrats a favour, Mr. Sanders could be returning it by moving his party too far left. Reaction to his health-care plank showed how strong his influence still is. Potential presidential candidates for 2020 – Elizabeth Warren, Cory Booker, Kamala Harris, Kirsten Gillibrand – all signed up to support it.

It was cheered on by socialists as well. David Duhalde, deputy director of Democratic Socialists of America, called it a "high-water mark" for the party.

While the Sanders ideal of universal coverage is laudable, it poses many risks for the party. Many Democrats fear it will hurt them in swing states in the midterm elections. For Republicans, the call for socialized medicine is music to the ears. One of the few things they still agree on is the need for tax cuts; the Sanders plan would hike the tax burden significantly.

The Republicans, with Senator Lindsey Graham heading the effort, are making a last-ditch attempt to repeal and replace Obamacare. They can now use the Sanders socialized-medicine plank as a weapon. If we don't act on Obamacare, they can argue, look what happens next. You'll feel the Bern. The socialist's tax burn.