It's not close to the same, it's exactly the same outcome.
In most cases yes. In a really close race voting L might result in an R winnning instead of voting D.
Imagine a race with 100 voters and three candidates, R, D and L. Say that 45 voters vote D, and 46 voters vote R. If the remaining 9 libertarians vote L the R wins. If they vote D the D wins.
In other words voting L subtracts one from the R total, but doesn't add one to the D total. In a very close race this might allow the R to sneak by.