David Jolly says he'll drop out if Rubio decides to seek reelection.
Heck will face Catherine Cortez Masto in the race to replace retiring Harry Reid.
Katie McGinty is trying to unseat Sen. Pat Toomey (R-Pa.).
The two Democrats square off in the runoff for retiring Sen. Barbara Boxer's seat.
Democrats argue Republicans have blocked gun control measures.
There has been speculation for weeks about whether Rubio will run for reelection.
Paul backed former Air Force Colonel Rob Maness in Louisiana's crowded field.
Kamala Harris made it into the November runoff.
Patty Judge was urged to run by party leaders and endorsed by the DSCC.
Grassley said he supports Trump's list of potential Supreme Court picks.