Yesterday, the Supreme Court struck down limitations that some states and the federal government had imposed on the
total amount of money donors could give to
all candidates. As you can see, that doesn't effect Texas since we pretty much have no limits for big money donors for state candidates.
Then there are "Super PACs" that you can donate to without limitation (Hello, Koch brothers.) They, in turn, can spend all that money in support of a candidate so long as it acts "independent" of that person's campaign.
It's all smoke and mirrors.