The Hill's Bob Cusack and Alexandra Jaffe preview Tuesday's Massachusetts Senate primary to fill the seat vacated by Secretary of State John Kerry. 

The Fairleigh Dickinson University poll shows Hillary Clinton with a 51-point lead over Vice President Biden among Democrats. 

The move could help Sanford regain his footing and improve Paul's standing in the early voting presidential state.

The pro-Democratic House Majority PAC goes right at former South Carolina Gov. Mark Sanford's (R) extramarital affair in their final ad, featuring a Republican woman who says she feels "betrayed" by his actions.

The National Republican Congressional Committee is demanding vulnerable House Democrats "support more freedom for working moms" in new Web ads, a sign the committee is trying to improve the party's standing with female voters. Read more...

Schweitzer leads former Montana Gov. Marc Racicot and Rep. Steve Daines (R-Mont.) in a hypothetical Senate match-up. 

The two are locked in a tight race to fill Sen. Tim Scott's (R-S.C.) old House seat.

The liberal congressman holds a double-digit lead in polls over Rep. Stephen Lynch (D) heading into Tuesday's vote.

Sen. Rand Paul (R-Ky.) will endorse former South Carolina Gov. Mark Sanford's (R) House campaign, according to CNN.

Paul's endorsement comes as he is gearing up for a potential presidential run, with an eye on early-voting South Carolina; according to the report, he is planning an extensive swing through the state in June. The endorsement could come as early as Tuesday.