There are 99 houses in 50 state legislatures. Any leftist amendment would require only 13 of these legislative bodies from 99 to defeat ratification. In other words, three quarters of the state legislatures must ratify or 38 states. If 13 legislatures fail to ratify the amendment is defeated. Since ratification by legislatures requires both houses to consent, only 13/99 are required. That is very close to 13%.
If the Congress of the United States elects to have the ratification procedures conducted by conventions rather than legislatures, the method of selecting the delegates to those conventions would be chosen by the legislatures. If only 13 legislative bodies out of 99 object to the method chosen by the other body because it is considered to favor a leftist amendment, there is no ratification forthcoming from that state.
By either procedure the odds of a liberal amendment getting past so many conservative legislative bodies in so many states is both arithmetically and practically remote.
Finally, this is only the last line of defense, there are innumerable steps along the way which make a "runaway convention" virtually impossible and render the need for the states to fail to ratify very likely superfluous.
