As Perot found out, if he's planning on getting matching funds for his campaign from the gov't (you know, that box on your tax return that says give so much of your money to the Presidential Campaign Fund?), he has to be on the ticket on election day.
Unless Trump is taking the high road and totally funding the campaign through contributions and his own fortune, it would not be good business to bail before the election. I assume that's what you meant by "close to the end" and not the party nomination.
By dropping out I meant and said "
bought out".
As for that little box on my tax return that says donate $1.00 to presidential elections, how many of the 245,273,438 adults (2014 census) of the USA check that box ?
I sure the "H" don't give the government one more red cent than I have to, much less another $1.00 to waste (again).

Did you ?
If every one of those adult Americans
worked and paid taxes checked that box, it would be a paltry $2.5 million.
And remember, only half of that buck would go to your party and you'd be supporting your opponent's party with the other half !

The 2012 campaign spending collected
$2,0651 MILLION DOLLARS, almost twice the amount of the 2012 $1.1 trillion Federal deficit 