At least 6.
Started out with the locker room talk scandal, but as Trump never presented himself as a plaster saint, it didn't carry any weight.
Next came the Russia. Russia, Russia. Trumps energy policies pulled the rug out from under the Russians, and Gen Mattis put a stop to their more egregious adventurism in the middle east so unless Putin was trying to undermine his own country, the charge against Trump made no sense.
As a by-product of the Russia fiasco, the involvement of the DNC and Clinton campaign in the Steele dossier became painfully obvious.
The impeachment effort filled headlines daily with people increasingly noticing that it served as an excuse for the House to do nothing else. I suppose that if you know that whatever the House does will be stopped in the Senate, and vice versa, there must be little incentive to even show up for work.
The involvement of the Chinese in stealing everything they could get their hands on in the US and adventurism abroad was met with resistance which the left tried, unsuccessfully to label as racism.
The virus problem was used as an excuse to shut down the fastest growing economy ever seen and mute Trumps claims to economic success. Used as an attack on Trump, it worked, but it worked sort of like setting off a giant stink bomb in a crowded elevator. The Chinese are trying to blame the virus on Trump. So far, no one is buying that. Trump is trying to get people back to work and is meeting strong resistance from the Dems who would prefer we all stayed home and starved.
Now comes the latest attack: The George Floyd riots. Note that the riots are happening in Donk controlled cities, and that the municipal administrations are for the most part, siding with the rioters. Black Lives Matter? Not really. If they did, the riots would be put down, the Antifas would be jailed, and black-owned businesses would not be burned out. Unemployed blacks are victims and as such are actively courted by the Dems. It's a good thing since the last time we had unemployment this high they elected their president 4 times in a row.
The riots being municipal level disturbances, the president has limited ability to jump in and put them down. It's a local problem after all. Somehow Trump is expected to come up with a Federal solution to local police problems while the house panders to black nationalists and tacitly supports their militia, Antifa. As such, I expect the left will be actively supporting the riots all the way through November with calls for more every time some thug of the right pigmentation gets shot by a cop in the commission of a crime. They will probably call for more if Trump gets reelected to protest “Vote Suppression”, something that can be investigated through his second term. Get out in the street, wave a sign, spread plague, burn your house down, and vote Dem. It's a safe bet that if a Dem becomes President, money for the rioters will dry up over night.
Every Monday, for the last 3-1/2 years, we've been told that the coming Friday would be the big day with Trump frog marched out of the White House in handcuffs. I'm still hearing this. I expect to hear it until 2024, unless the election turns into a huge landslide of voters fed up with Dem shenanigans who hand Trump a second term with both the House and Senate. In that case, the republicans will revert to form and spend most of their time attacking each other.