All Presidents do things for personal political benefit and it has never been deemed impeachable

Wall Street Journal Editorial:

...
House Democrats are going much further and declaring that Mr. Trump’s acts are impeachable because he did them for “personal political benefit.” He isn’t accused of corruption per se. His Ukraine interventions are said to be corrupt because he intended them to help him win re-election this year. In other words, his actions were impeachable only because his motives were self-serving.

Think about this in the context of history and as a precedent. Every President has made foreign-policy decisions that he thinks may help his re-election. That’s what President Obama did in 2012 when he asked Dmitry Medvedev to tell Vladimir Putin to ease up on missile defense until after the election. Mitt Romney was criticizing Mr. Obama for being soft on Mr. Putin, and Mr. Obama wanted a political favor from the dictator to help him win re-election.

Was Mr. Obama’s motive also corrupt and thus impeachable? We can guess what Mr. Romney thought at the time, but he didn’t say Mr. Obama should be impeached. He tried to defeat him at the ballot box.

As 21 Republican state attorneys general explained in an important letter to the Senate on Wednesday, “It cannot be a legitimate basis to impeach a President for acting in a legal manner that may also be politically advantageous. Such a standard would be cause for the impeachment of virtually every President, past, present, and future.”

The AGs add that the “House’s corrupt motives theory is dangerous to democracy because it encourages impeachment whenever the President exercises his constitutional authority in a way that offends the opposing political party, which is predisposed to view his motives with skepticism and motivated by its own motives to regain that very office.”
...

The Senate should reject this theory out of hand.  You could also make the same argument about the Democrats' impeachment efforts being based on "corrupt motives" for political advantage.  In fact, that theory is much more applicable to what Schiff et.al. are doing.  They are trying to impact the 2020 election to benefit their party.