Image copyright Getty Images Image caption US mid-term elections are just a year away

In American politics, life comes at you fast. An election is won and office is achieved. Opponents run for the hills. But for how long?

French presidents last five years. British prime ministers can go on and on. But in the land of the free, nothing lasts.

America is a nation of strivers, and sitting presidents are not exempted from that general rule.

With so much of the news coverage of Donald Trump's 100 days in office focusing (rightly) on his achievements and his failures, I wanted to look as well at the chances his opponents have to damage him, soon. I wanted to look, in other words, at the mid-term elections of 2018.

Yes, sirree: we are just one year from a set of elections that could do Mr Trump great damage. A third of the US Senate will be up for election and the whole of the House of Representatives, whose members only serve two years at a time.

Mid-term elections do not excite most Americans. Many voters who manage to get interested enough to vote in a presidential year simply fail to show up in the off-years.

Party support on Capitol Hill is vital

President Obama's chief strategist and friend, David Axelrod, brought the subject up with a rueful tone when I talked to him on this US visit.

"[Obama] got re-elected, sure," Axelrod told me. "But after 2010 everything was a struggle with the Congress."

His point was clear - Obama was a successful president, but could have done so much more if he had held on to party support on Capitol Hill, particularly in the latter years of his presidency.

Image copyright Getty Images Image caption Obama could have done so much more if he had not lost control of the Senate and House, says David Axelrod (right)

Defeats matter because under the US system, the two houses of Congress have a great deal of power. They can block a president from legislating. They can cut off money for funding for his projects. They can harass his officials. Vote down his Supreme Court choices.

And, yes, in extreme cases they can impeach him, begin the process of throwing him out of office. If you oppose the inhabitant of the White House and suspect him of serious misdemeanours, you would be keen to vote in 2018.

Could Donald Trump's presidency be hit by enough scandal by next year that those Republicans who stick with him go down? Well, it's hardly impossible, is it?

Democrats gearing up for 2018

Democrats hope that the travails of the Trump presidency might allow them to torpedo the enterprise after only two years. I met Democrats during a brief but fascinating trip to Texas who are seriously gearing up for 2018.

On the outskirts of Fort Worth on a Sunday morning, I watched Congressman Beto O'Rourke work a crowd of several hundred who had turned out to cheer him in his effort to be the candidate to try to unseat the Texas Senator and former presidential hopeful Ted Cruz.

Image copyright Getty Images Image caption Democrat Beto O'Rourke has his sights set on unseating the Texas senator and former presidential hopeful Ted Cruz in 2018

Does the congressman have a chance? Democrats have not been winners in state-wide elections in Texas for many a long year but that is the point - perhaps 2018 is different.

Time for a reality check.

First, the House of Representatives is a gerrymandered institution - the districts in many states have been carved out in order to keep parties in power rather than have genuine toss-up elections.

Take a look at the map of congressional Districts around the Texan state capital Austin. I walked down a street where individual businesses and homes had been picked off and placed in different districts depending on the perceived political views of the inhabitants. These seats do not change hands; some are barely contested.

It is also true that most of the Senate seats up for re-election in 2018 are held by Democrats: they are defending this year, not attacking. Yes, the Texas seat of Ted Cruz would be a major prize but in other places, including places where Trump polled well, the Democrats will be fighting to hang on.

And anyway, the Democratic party is still in a heck of a mess.

I had lunch in Austin with Steve Rossignol of the American Socialist Party. He was brutally frank about the state of the American left: how Black Lives Matter folks don't see eye to eye with old-fashioned white union guys; how they in turn are not interested in illegal immigration.

We didn't even get to transgender bathrooms. But this fissiparous crowd is the same crowd Congressman O'Rourke is trying to marshal into some kind of cohesive force.

As Americans say, good luck with that.

Still over a year to go

James Henson founded the University of Texas/Texas Tribune Poll.

So what is his prediction for the mid-terms in this state and beyond, I asked.

He looked pained.

But pressed, he said he thought the Democrats would gain seats, though not enough to win control of Congress.

Well, that's a safe view. The Democrats have a little over a year to prove him wrong and mess up the Trump White House.

I personally think they might win the House of Representatives but not the Senate.

Donald Trump might be tempted to look for deals with a Democratic House of Representatives and might be more successful than he has been with members of his own party.

After all, wasn't Donald Trump a Democrat once?

But that's another story.