The battle to fill an open U.S. Senate seat in Texas is heading for a runoff election for each party.

On the Republican side, the race is down to Texas Lt. Gov. David Dewhurst and Tea Party-backed former Texas Solicitor General Ted Cruz.

In Tuesday's Texas primary, Dewhurst had the lead but failed to get the majority of the votes needed to beat Cruz.

Now, experts say the candidate voters perceive as more conservative will likely win.

There will also be a runoff between the Democratic candidates -- former state Rep. Paul Sadler against Grady Yarbrough.

Texas hasn't elected a Democrat to the U.S. Senate since 1988.