Candidacy? Trump doesn't need to announce his candidacy. Donald Trump is going to be re-installed as president come October don't you know??? Just ask any Q-er, they know they know. All that Trump need do is to sit back and wait for October, and his people will do all the rest.
But if October doesn't work out, haha, then Trump will decide after the midterms to run. If democrats suffer a dreadful 2022 then Trump will see that loss as his victory with convincing Trump that the voters are with him, so Trump will definitely announce. However, if democrats actually take more seats in the house and in the senate come 2022 and the republicans fail, then I doubt that Trump will run.
Another factor, the other wannabe presidential hopefuls in the republican party. I doubt that the republican wannabes in the party will simply allow Donald Trump to waltz in and take over the process. There will be congressional republicans and republican governors that want that job and they will need to decide if they dare challenge Donald Trump.... or roll over and play dead.
But lets talk about Joe Biden.
Already the republicans are trying to turn Afghanistan into Biden's Benghazi. Don't believe me??? Then just tune into Fox News for ten minutes. Afghanistan is their one and only story. If republicans take the senate and or the house, you can bet your life that republicans will repeat and turn the Hillary Benghazi into the Joe Biden Afghanistan, with hearing after hearing after hearing. By the time republicans in congress and Fox News are finished with their Biden-Afghanistan hearings you will think that it was Joe Biden who started the whole Afghanistan thing in the first place 20 years ago. Joe Biden alone and all by himself.