It all comes down to wins and losses, lets look at what each team has left.
KSU H OSU, @ ISU, H UT current record 3-0
OSU H ISU, @ KSU, H UT, @ OU current record 2-0
UT H ISU, @ KSU, @ OSU current record 1-2 loses tiebreaker to KSU & OU
OU H OSU, current record is 2-2, loses tiebreaker to ISU and KSU, but has it over UT
ISU H KSU, @ UT, @ OSU current record 3-0 holds the tie breaker over OU.
ISU needs to go at least 4-2 the rest of the way to make the championship game.
UT has to win out to have a chance.
OU has to win out.
KSU has to go 4-2.
OSU has the hardest path as they have to play the other four teams in the league that can win it.
If ISU or KSU win 5 of 6, they are in no matter what, unless OSU loses less than two, thereby knocking out either ISU or KSU.
This is all assuming that there are no major upsets by anyone, the only team that looks capable of pulling that off is TCU, and both KSU and ISU have already beaten them.