The democRAT-controlled House can use whatever they like for charges to impeach Trump.
But there are downsides that are political too.
First the Senate, probably won't convict.
Second, the voters will see whether the democRATS are being frivolous or serious with their impeachment effort. The 2020 election looms large.
Impeachment is constitutional even if the charges are based on partisan politics.
If that is true, why does the constitution outline the rules? Treason, Bribery, or other high Crimes and Misdemeanors are the only reasons outlined in the constitution for a basis for impeachment. Not whatever the Democrats decide is a good reason minus any crime. If they had uncovered even a misdemeanor, then there could be a political basis, but as far as we have seen - not even that has been found.