Denver, Colorado (CNN) - President Obama and former President Bill Clinton are on opposite sides of a divisive Democratic Senate primary and a former pro-wrestling executive could take a big step toward winning election to the Senate - those are just two of the storylines as Colorado, Connecticut, Georgia and Minnesota hold primary contests Tuesday.
In Colorado, incumbent Sen. Michael Bennet is battling for his political life as he faces a primary challenge from former state House Speaker Andrew Romanoff. Bennet was plucked out of political obscurity early last year when Colorado Gov. Bill Ritter named him to replace then-Sen. Ken Salazar, who stepped down to serve as interior secretary in the Obama administration. Bennet was superintendent of the Denver school system at the time.
As sitting senator, Bennet has the backing and help of the national party and the White House. Obama headlined a fundraiser for Bennet in Colorado early this year and last month he recorded a robocall and sent out an e-mail in support of the senator.
But Romanoff has his own big-name endorsement. Earlier this summer Clinton announced he was backing Romanoff, whom he's known since 1992. Romanoff also supported Hillary Clinton's 2008 Democratic presidential bid. Clinton's voice appears on a robocall urging Colorado Democrats to vote for Romanoff.