Did you know that you must be registered as a Republican to vote for Trump in the primary?

That, specifically, is for a state that has a "Closed Primary"...but even in some of those states you can be registered as a Conservative, but still vote in the Republican Primary. It is true in some states, but not in states where they have "Open Primaries", where anyone can vote in the Primary Election so long as they are registered to vote. Also, not all state have Primaries, some have Caucuses.

And some states have "Blanket Primaries", where you must chose which Primary you would like to vote in, but you don't have to change your party affiliation to do it.

For the Primary in Arizona, it is considered semi-closed. Unaffiliated voters may choose which party’s primary they will vote in (like a blanket Primary), but voters registered with a party affiliation can only vote in that party’s primary (like a closed Primary).”

In West Virginia, only the Democrats have a Closed Primary.

In Alaska, only the Republicans have a Closed Primary.

If there is a runoff Primary in Texas, you can only vote in the Runoff Primary of the Party you initially voted for in the first place. In other words, if there is a Runoff between two Republicans, but you voted for the Democrat, you can't vote in the Runoff Primary between the two Republicans.

https://ballotpedia.org/Open_primary

https://ballotpedia.org/Closed_primary

https://ballotpedia.org/Blanket_primary

https://ballotpedia.org/Top-two_primary

Not necessarily. Some states have "closed primaries" where only registered party members are allowed to vote. Other states have "open primaries" where any registered voter can vote.

You do have a point however that Trump, who draws most of his support from infrrequent or first time voters, is at a disadvantage in closed primary states because not all of those people will be able to vote in the primary.

Not in my state, you pick which primary you're voting in, however you do have to stay with that party though any runoff primary elections.

Like many Democrats in Texas, especially when the Democratic nomination is pretty well decided, I often vote in the Republican primary to have more influence in who will be opposing the candidate that I actually will be voting for. So it's pretty likely I'll be voting for someone who I feel can win Texas but eventually lose to a Democrat, and also someone who is not Trump. I generally only vote in the Democratic primary when there's no clear frontrunner and I have a candidate I strongly prefer over others.

Thats true in many states. I wanted to vote for Ron Paul in 2004 but could not since I am not a Republican. I ended up not voting at all. So if that happens to me, imagine how many millions of people are in states that force you to be registered in a particular party and also dont vote. Thats one reason this whole process is terrible. So I was so disgusted, I became "unaffiliated" but in 2012 the Election Board said I had to register as Repub or Dem to vote in that primary which I did.

If you're a Democrat or an Independent (as many Trump supporters are), and you want to cast your vote for Trump, be sure to re-register as a Republican or you will not be able to vote as you choose to in the primary. Deadlines for changing your registration vary by state, so be sure to check prior to the primary. You cannot vote across party lines in a primary election.Very important! I hope Trump will mention this on TV--many people, particularly those who haven't voted recently, are unaware of these dates.

Only if it's a closed primary.

Yes, but I usually vote Democrats!

Actually, that depends on the state you live in. Some states only let voters in certain parties vote for that party.

Yes if you live in California. Not sure on the other states

yes