Her fall campaign schedule begins with Sen. Tom Harkin's annual steak fry.
The Texas governor will visit the early presidential primary state on Friday.
The key question is who might emerge to give Clinton a serious challenge from the left.
Differing tone could provide clues for the divergent trails the senators are forging.
The Texas senator defended Perry after the governor was indicted Friday.
Santorum is making the three-day trip with Bob Vander Plaats and Foster Friess.
The governor says his decision will come "by the end of this year or the beginning of next."
Presidential aspirants are weighing in on the ongoing tensions in Ferguson, Mo., staking out positions that could reverberate in 2016.
Paul warned of a "systemic problem with today’s law enforcement."
Sen. Ted Cruz on Thursday criticized the arrest of reporters in Ferguson, Mo.