There are a few reasons why she is still considered "their best choice".
1. TPL's husband was LHL's private secretary and she is obedient.
2. They would have a tough time explaining why she steps down, considering that she is young, one-term, had publicity on "how hard she has been working" last 4 years.
3. It would essentially be admitting that they made a mistake in 2011, taking into account all the publicity about her leading up to polling day. They never like to lose face or admit they are wrong.
These are the MPs who have so far "resigned".
If your theory is correct, then none of the first term MPs will be on the list?
) AMK GRC MP Inderjit Singh
2) Tampines GRC MP Irene Ng
3) Tampines GRC MP and Ex-Minister Mah Bow Tan
4) Moulmein-Kallang GRC MP and current Transport Minister Lui Tuck Yew
5) Bishan-Toa Payoh GRC MP Hri Kumar
6) Bishan-Toa Payoh GRC MP Zainudin Nordin
7) Bishan-Toa Payoh GRC MP and Ex-Minister Wong Kan Seng
8) Sembawang GRC MP Hawazi Daipi
9) AMK GRC Seng Han Thong
10) West Coast GRC Arthur Fong
11) Sembawang GRC MP Ellen Lee
12) East Coast GRC Raymond Lim
13) Choa Chu Kang GRC Alvin Yeo