Markets have been a bit concerned around the impeachment procedure that the Democrats started against Trump.
The Democrats do not think they have much chance of winning the US presendential elections next year. They have waited for three years to hope a great candidate would pop up out of nowhere but it did not happen. Trump is surviving and the US economy is still in a solid state. The Democrats needed a good candidate or a stock market crash to be able to easily win the elections in November next year. Currently, they will probably lose against Trump. So, they had to come up with another strategy than by just winning it on quality.

Joe Biden is the sacrifice
The Democrats are going for the sacrifice option. They are sacrificing Joe Biden and try to bring Trump down with him. They have lost all confidence in Biden and think that the chance of bringing Trump down is even bigger than Joe Biden to win the elections next year. As has been everywhere in the news lately, Trump tried to use his presidential powers to influence the elections of next year by requesting Zelenskiy, the Ukrianian President, to investigate Bidens actions. Biden had requested to fire a prosecutor in Ukraine. At the same time as this prosecutor was investigating an issue with a company, of which Bidens son was a board member. It is not yet proven that the two are connected, but it does not look good for Biden.
The Democrats started an impeachment procedure. Because they started this whole thing, also Bidens actions will be investigated in further detail. This will most likely not help Joe Biden. But if the democrats can impeach Trump or can let him look very badly, they are happy to sacrifice Joe Biden.
Elisabeth Warren is the goal
The Democrats are putting their money on Elisabeth Warren. She was already doing well in the polls compared to Biden and the Democrats see her as their only option to win the elections. If Trump can be impeached or looks very bad, the Republicans have not really any alternative. It will be an easy win for Elisabeth Warren. Elisabeth Warren is a massive climate fighter and is willing to let the economy pay very hard for it. A Warren presidency will be very bad for the economy and the stock market, if she at least does some of the things she has been promising. She wants to overnight move away from all fossil energy sources. Politically impossible and economically as well, but if she pushes for it, it will affect the markets and the job security for a lot of Americans.
Chances of impeachment
An impeachment can only succeed if it passes the House of Representatives and the Senate. In the House there needs to be a majority. It will likely pass the House as the Democrats are in the majority. In the Senate the impeachment needs to be supported by at least two third of the votes. The Republicans own the Senate so this is very unlikely. Republicans have so far always supported Trump. Only if Trump really did something outrageous, Republicans might turn against him. Anyway, for the moment an impeachment procedure that passes both the House and the Senate can be expected to be very unlikely. Next to that, it is also unlikely that Trump will resign himself because of any scandal. He will stay in the Oval Office till the end.
What if there is an impeachment?
Trump will not be president anymore and Mike Pence takes over until the elections in November next year. Obviously the Democrats will have a great chance of winning in the case of an impeachment..