Winning a political office is ultimately a ground game, not a TV game although TV must be in the mix with at least TV commercials and interviews are necessary, too. However, if one only has TV appearances, that person won't win.
Think of it this way:
Most Republicans work for a living (unless retired and at home all day). They stay at work all day and come home and relax, eat dinner, talk to/play with the kids and fall in bed to begin another day tomorrow. Their work keeps the family operating and that is their main concern.
Millions of working families may not know which day the voting primary is and they miss it. The only way to get these people to the poll is to contact them to remind them to vote. The candidate can mail literature and that may or may not get read and if read, the reader may not notice the date for voting and besides, the reader is pressured for time since the car needs an oil change or Johnny has to be taken to the dentist or groceries have to be bought and a zillion other daily living things must be done.
Getting the vote out to the poll is the most important part of a campaign. All other campaign action is useless if the voter doesn't vote. Millions of voters don't vote in a primary because they don't know it is happening. The turnout in November for the general election has millions more voters than a primary. If your candidate didn't win in the primary, your candidate isn't on that November ballot. The bottom line, then, for a candidate, is to get their voters to the primary election.
How do candidates know which voters to contact for the primary election?
In a primary election, a voter must choose to vote in the Democrat Primary or the Republican Primary. The master voter list of a county has stamped Democrat or Republican by the name of the person who votes in the primary election. That list is available to candidates. A Republican candidate gets those lists and there are the voters who voted Republican in the last Republican Primary.
That Republican list is gold to a candidate as those voters will turn out if reminded to vote on primary day. The candidate gets his/her message out to those voters to convince the voter to vote for him/her.
So, solid Republican primary voters are known to candidates if they get the county primary list of voters from the last primary election. I got those lists for candidates I was helping and made a mail list of voters by combining the names of family members and their mailing address so mail would go to the one address of families.
Most people don't know the amount of work that goes on behind the scenes during the primary season. Those voter lists are right now being put together if a candidate is smart.
Jeb is running on empty. All hs has going for him is that deep treasure chest.