U.S. Sen. Mary Landrieu and her main Republican challenger, Congressman Bill Cassidy, have officially signed up for Louisiana's Nov. 4 election.

The three-day qualifying period opened Wednesday and runs through Friday. Contenders vying for any elected office have to pay fees and sign paperwork.

Landrieu, a Democrat seeking a fourth term, talked of her seniority and leadership position, saying Louisiana voters shouldn't give up that clout.

Cassidy described his effort to oust Landrieu as crucial to returning the U.S. Senate to GOP control. He repeatedly linked Landrieu to President Barack Obama, who is highly unpopular in Louisiana.

Republicans showed up with "Air Mary" signs, a dig at the scrutiny Landrieu has faced for billing private chartered planes to her Senate office when she used the flights to attend campaign fundraisers.

Also signing up on Wednesday, Libertarian candidate Brannon McMorris of Denham Springs.

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