What is past tense of the word plead?

The past tense of plead is pled or pleaded, depending on the context.
According to several reference sources, pleaded is the past tense and past participle when referring to an emotional way of begging someone, e.g. The anguished mother pleaded via the media for her wayward daughter to return home.

It should be noted that pleaded is the only form accepted by Black's [Law Dictionary].

'Pled' is a colloquial term which has become more acceptable in recent years, but is still not the preferred choice. However, as English is an evolving language, it means that, among the lay crowd "pled" has become more common. According to at least one reputable source, both 'pleaded' and 'pled' are now two correct forms

You may choose to accept either answer, however in legal circles it appears that the only acceptable form is "pleaded".

It is not remotely acceptable to say the past tense of "plead" is "plead."