Cassidy (R) outraised Sen. Landrieu (D) by $500,000 in last month and has more in the bank.
The GOP doctor says allegations he wrongly billed LSU while in Congress are bogus claims.
The former Hewlett-Packard CEO ran unsuccessfully as a Republican against Sen. Boxer in 2010.
Mitt Romney would tie Hillary Clinton in a hypothetical matchup.
"Something is wrong with criminal justice in America," the senator wrote.
The Arizona Democrat is challenging the disqualification of 133 ballots.
Louisiana Dem says her GOP opponent voted to cut funding for schoolchildren to pay for it.
Warren will also visit the West Bank and Jordan in a move stoking 2016 speculation.
Finalists include Brooklyn, N.Y., Philadelphia and Columbus, Ohio.
Tea Party favorite drew applause from a crowd that included mega-donor Sheldon Adelson.