And they are still sticking with him now even though all elections are over and they won't control presidency, house, or senate.
It seems a bit premature to call how many within the GOP 'stick' with Trump - he hasn't even left office yet.
I think there's a party reckoning coming, and it won't be pretty. The entered 2016 in full control of the House, Senate and WH. In 2018 they lost the House. In 2020 they lost the senate and WH. They've lost Georgia and Arizona and gave back the states Trump so narrowly won in '16. Trump is no longer the teflon 'winner' he's promoted himself as. Meanwhile, at least four major lawsuits are proceeding and he'll lose protection from prosecution in two weeks, and by most accounts he's milking his supporters for donations in a frantic race not to default from some $320MM in personally-guaranteed loans which will come due in the next few years.
Trump won't shut up after leaving office - of that I am convinced. But I think it's an open question how durable his support is. His endorsements and campaigning didn't help Perdue or Loeffler. Arguably it may have hurt them. Hopefuls (e.g. Cruz) are in a crushing dilemma where they have to do dumb-a** stuff to appease Trump but which will polarize them for any state or national election. Some may look at Loeffler's loss and conclude it's in their political interests not to go down the Worship-Trump rabbit hole.
tl;dr - I'd wait until summer 2022 before declaring how durable support for Trump really is.