The impeachment process is spelled out in the Constitution and involves "high crimes and misdemeanors." So yes, it's a legal process. If the Democrats take back the House but not the Senate they(the House) could vote to impeach but it's the Senate that tries and convicts. Right now it looks like 5 Democrat senators in red States are in danger of losing their election. So good luck getting the majority needed to convict and remove Trump. And if they do it for any reason other than having definitive proof he committed a crime expect a huge backlash. In case you hadn't noticed Trump's approval ratings have gone up. I doubt he'll get re-elected because the Democrat base is so energized but if the economy does well he has a shot. Why he would want to put up with the foolishness is beyond me other than a massive ego.
A Democrat on FOX News pointed out something that has got him in hot water with MoveOn.org and others. We're moving to automation of many jobs that will eliminate millions of them. How can we keep importing millions of low skilled foreigners who won't have upward mobility and will be competing with citizens for low skilled service jobs? Said that's coming in 5 to 10 years. Democrats want the votes, but how can you sustain caring for millions with no work? Sorry, off topic, but it's something I wanted to get in because suddenly all of those illegals, with more coming all the time, are about more than just illegally being here.
