my If，Else和Elif语句的“语法错误”（Python）

Question

这是我的代码：

print "Hello, and welcome to the Slightly Interactive Autobiography of Robbie Wood."
print "Lets get started, shall we? What chapter would you like to read first?"
chapter = raw_input("Please type either 'Chapter 1', 'Chapter 2' or 'Chapter 3': ")

if chapter = "Chapter 1":
    print "Chapter 1"
    print chapter_one

else chapter = "Chapter 2":
    print "Chapter 2"
    print chapter_two

elif chapter = "Chapter 3":
    print "Chapter 3"
    print chapter_three

elif:
    chapters = raw_input("Please type either 'Chapter 1', 'Chapter 2', or 'Chapter 3': ")

# Variables - Chapters
chapter_one = "text here..."
chapter_two = "text here..."
chapter_three = "text here..."

下面是来自终端的确切错误消息：

Last login: Fri Sep  7 17:22:59 on ttys000
Robbies-MacBook-Pro:~ robbiewood$ /var/folders/y6/kx37qgbs34124ztdgb4tphs00000gn/T/Cleanup\ At\ Startup/autobiography-368756862.498.py.command ; exit;
File "/private/var/folders/y6/kx37qgbs34124ztdgb4tphs00000gn/T/Cleanup At Startup/autobiography-368756862.497.py", line 9
    else chapter = "Chapter 2":
               ^
SyntaxError: invalid syntax
logout

[Process completed]

有人能帮我解决这个问题吗？我是一个初级的Python程序员，我正在为一个学校项目编写一本“稍微互动的自传”。