GOP Victorious in South Dakota, Montana Primaries

The Republican push to take control of the U.S. Senate is gaining strength following Tuesday's primary results.

In South Dakota, former Gov. Mike Rounds won the Republican nomination. Rounds is considered a favorite to win a seat held by retiring Democratic Sen. Tim Johnson.

In Montana, Republican Rep. Steve Daines won the Senate nomination.

Analysts call these candidates "top-tier nominees" who have support from Republican establishment and Tea Party leaders.

In Mississippi, Sen. Thad Cochran and Tea Party challenger Chris McDaniel are still looking at a possible run-off on June 24.

Republicans need six new seats to control the U.S. Senate.