Political strategist Steve Bannon has warned Republicans to rally around President Donald Trump – or face losing up to 40 seats.

Mr Trump’s former chief strategist said that if the autumn mid-term elections were to be held today, he believes the party could cede their majority to the Democrats.

Mr Bannon said he is convinced that the Democrats would then pursue impeachment.

Steve Bannon
The former strategist’s relationship with the president soured in the past year (AP)

Arguing that there is still time to turn the situation around, he is launching a group, Citizens of the American Republic, to pitch the election as a vote to protect Mr Trump from that outcome.

Mr Bannon said: “You can’t look at this as a mid-term and you can’t run it out of the traditional Republican playbook. If you do that, you’re going to get smoked.”

The effort is a test of Mr Bannon’s sway in the party a year after he was removed from his White House post.

His relationship with Mr Trump soured after a tell-all book published in January included searing quotes of Mr Bannon portraying the president as undisciplined and criticising his son, Donald Trump Jr.

Steve Bannon
Mr Bannon said he believes the Democrats will attempt to impeach the president (AP)

His stock fell further after he backed Alabama Republican Roy Moore’s Senate campaign even after decades-old sexual misconduct allegations emerged. A reliably Republican senate seat subsequently turned Democratic.

As he attempts a comeback, Mr Bannon acknowledged the challenges he faces, including an invigorated Democratic base.

Less than three months from election day, Democrats need a net gain of 24 seats to retake the House, and the party is increasingly bullish about its chances after strong turnout in a series of special elections.

Mr Bannon said Republicans can gain ground if they focus on turning out Trump supporters.

Steve Bannon
The former White House chief strategist has said the Republicans could lose their House majority (AP)

He said: “This is not about persuasion. It’s too late to persuade anybody. We’re 90 days away from this election. This is all about turnout and what I call base-plus.”

While Mr Bannon makes his move, many Republicans view holding the House as an uphill battle.

Mr Bannon said his new venture will focus on rapid response and polling with the goal of framing the election as an “up or down vote” on Donald Trump and impeachment. He is also releasing a movie about the president, Trump@War, geared at Trump supporters.

Mr Bannon said he was being backed by private donors, but he did not detail who was funding the effort or how much he had raised. He said his efforts were independent of the Republican National Committee, the White House or a Trump-supporting super political action committee.

In keeping with his mid-term mission, Mr Bannon defended the president on both policy and style, arguing that the president had an economic record to run on and has been making the right pitch on the campaign trail.

On trade, the former strategist backed the president’s aggressive tariffs, which have drawn criticism in agricultural states crucial to Mr Trump’s victory. He argued they were a key part of the president’s nationalistic economic strategy.