Colorado Democrats will decide on whom to choose as their Senate candidate "irrespective of endorsements," incumbent Sen. Michael Bennet (D-Colo.) said Tuesday.

Voters head to the polls Tuesday to cast their ballot in the contested primary between Bennet and former state House Speaker Andrew Romanoff, who's waged a Democratic primary challenge from Bennet's left.

Both candidates boast top endorsements, pitting President Obama (who endorsed Bennet) against former President Bill Clinton (who endorsed Romanoff).

Bennet said he's happy to have the president's support, but downplayed the role the endorsements would play in voters' decisionmaking.

"I think it helps — I'm very proud to have his support — but I think the people of Colorado are going to make this decision irrespective of endorsements," he said during an appearance on MSNBC.

Romanoff has surged in recent days, raising the prospect of another defeat for a Democratic candidate favored by the White House. Obama had backed Sen. Arlen Specter (Pa.), who lost a Democratic primary to Rep. Joe Sestak in Pennsylvania. The White House was also embarrassed when Democratic Attorney General Martha Coakley lost the special election in January to fill the Senate seat left vacant by the late Sen. Edward Kennedy (D-Mass.).