Donald Trump has grabbed onto a proposition that will play well both with his base and with whatever pool of undecided voters may remain out there: term limits for members of Congress.

Speaking in Colorado Springs on Tuesday, the Republican nominee said that passing a constitutional amendment that would keep members of the House of Representatives and of the Senate from lingering too long was part of broader plan to “drain the swamp” in Washington.

He also sketched out steps to tame the lobbying industry in Washington, a pledge that President Barack Obama made before he took office for the first time and which he largely failed to deliver.

Mr Trump is expected aggressively to make the case at his third and final debate with Hillary Clinton on Wednesday night that only he has what it will take to end what he called “the cycle of corruption” in the nation’s capital. He will add that the Clinton family were part of the problem.

“If I'm elected president, I will push for a constitutional amendment to impose term limits on all members of Congress,” Mr Trump said at an afternoon rally in Colorado, a battleground state he appears increasingly unlikely to win. “They've been talking about that for years. Decades of failure in Washington and decades of special interest dealing must and will come to an end.”

The idea of ending the present system of open-ended careers on Capitol Hill has been floated from time to time and even became the subject of a Supreme Court case twenty years ago.

Moreover, the notion of term limits - as they apply now to presidents who can only serve two terms - is immensely popular with many Americans, especially at a time when the US Congress and Washington in general are held in historically low esteem.

But while it may make political sense for Mr Trump to try to lead the term-limit bandwagon, he will also know that the chances of it ever arriving at the station are extremely slim. Any amendment to the US constitution requires the support of two thirds of both chambers of Congress before it can even start to get anywhere.

While ordinary voters might support it - a 2013 Gallup poll showed an astonishing 75 per cent of Americans, including both Democrats and Republicans, voicing support for term limits - getting those two-third majorities would be singularly problematic. It means asking members of Congress to sign papers consigning them to joblessness. That is an unlikely proposition.

In that sense, it may be a fairly meaningless proposal from Mr Trump, but one that will nonetheless resonate well with voters. He has built his campaign partly on the notion that he does not belong to the political establishment and he will find ways to sweep it out.

Under his plan, members of the House would be allowed to serve three two-year terms only, while members of the US Senate would be limited to two 6-year terms. That still means someone who transitions from one chamber to the next could be in Washington for eighteen years.

His anti-lobbyist proposals are also likely to be well received. Mr Trump is saying he would find ways to ban members of Congress and officials who have served in the executive branch of the government from engaging in any kind of lobbying in Washington for five years upon leaving office or their positions.