Sen. Claire McCaskill (D-Mo.) faces a tough campaign for re-election, including a torrent of negative advertising even before the GOP primary to challenge her is held.

But she does have a massive advantage in fundraising, Missouri's Springfield News-Leader reports. Beyond the $5 million of her own cash, McCaskill leads all her Republican rivals in Missouri fundraising by $450,000 and in out-of-state fundraising by $2.2 million.

Her top donor is Emily's List, a pro-choice Democratic political action committee. She's also attracted backing from firms that do business in the state, including a PAC run by Boeing.

McCaskill launched her first TV ad, in which she goes after "special interests" for their spending in the race, in February.

Polling predicts a tight general election between McCaskill and her eventual GOP opponent.

10 more election stories from beyond the presidential field:

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Dick Lugar's Lead Over Primary Opponent Richard Mourdock Now In Single Digits [Politico]

Rep. Louise Slaughter Gets First Serious Challenge In Years [Rochester Democrat And Chronicle]

Marco Rubio Rushes Publication Of Autobiography [The Miami Herald]

Mazie Hirono Opens Campaign Headquarters [Hawaii Reporter]

Wisconsin Senate Hopeful Campaigns With Pig Named Mr. Favors [AP]

Tommy Thompson Tries To Reinvent His Image [The Wisconsin State Journal]

Eric Cantor Claims Senate Dems Are Obstructing Bill To Help Their Campaigns [The Hill]

Donald Payne Jr. Running To Replace His Late Father [Roll Call]

Rep. Makes GOP Ballot To Challenge Kirsten Gillibrand [Patch]

CORRECTION: The headline originally stated that McCaskill has outspent her rivals. It has been corrected to reflect the fact that she has outpaced her rivals in fundraising, not spending.

Earlier on HuffPost: