I am not a fan of the term "conditional election" as I believe that "election" has been misunderstood and polarized but the actuality of human choice within the framework of God's complete foreknowledge can be biblically established. As usual there are lots of "proof texts" for this position as well as it's antithesis: Here are a few that, I believe, establish the scriptural basis from which to reason.
God knows the end from the beginning. If we do not tack on any limitations to this statement and let His foreknowledge be as infinite as He is, then He can easily have foreknown each and every human choice before He created anything. Some believe that such foreknowledge eradicates the possibility of actual choice but that conclusion is by no means inescapable.
Remember the former things of old: for I am God, and there is none else; I am God, and there is none like me, Declaring the end from the beginning, and from ancient times the things that are not yet done, saying, My counsel shall stand, and I will do all my pleasure: - Isaiah 46:9-10
Election is according to God's foreknowledge. This is clearly stated in a few places. Peter most directly states it and Paul indicates a progression starting with foreknowledge, through calling, and ending with glorification. Some will try to narrow the definition of "foreknown" to the knowledge born of personal intimacy or some such thing but this does nothing to disconnect the possibility of human choice from the equation.
Elect according to the foreknowledge of God the Father, through sanctification of the Spirit, unto obedience and sprinkling of the blood of Jesus Christ: Grace unto you, and peace, be multiplied. - 1 Peter 1:2
And we know that all things work together for good to them that love God, to them who are the called according to his purpose. For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren. Moreover whom he did predestinate, them he also called: and whom he called, them he also justified: and whom he justified, them he also glorified. - Romans 8:28-30
The invitation is genuine. There are many commands and invitations to turn away from sin and turn toward the living God which are direct or implied. These all lose their genuineness if the manner of our response is pre-programmed rather than foreknown. For instance, God has commanded all men everywhere to repent (Acts 17:30) but, if He actively withholds the ability to repent from some, there is little purpose in the command to them.
Come unto me, all ye that labour and are heavy laden, and I will give you rest. Take my yoke upon you, and learn of me; for I am meek and lowly in heart: and ye shall find rest unto your souls. - Matthew 11:28-29
Condemnation is also linked to choice. If the following passage is read with the understanding that all the "loving", "hating", "believing" (or not), "doing", and "coming" are not acted upon human choices but are, instead, inescapably pre-programmed activities then the explanation of the nature of the condemnation becomes garbled.
He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil. For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved. But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God. - John 3:19-21
The Prodigal Son. Reading this parable with the understanding that the younger son did not actually choose to demand his portion of the inheritance, did not choose to squander it, did not choose to return to the father in repentance, etc. not only makes the story nonsensical but also inapplicable: We would have the father rejoicing in the recovery of what he had lost on purpose and then "found" again.
Imagine this re-worked Scripture being the case: "He that believeth on the Son (because God grants the ability) hath everlasting life: and he that believeth not the Son (because God withholds the ability) shall not see life; but the wrath of God abideth on him.".