Democrats have successfully recruited a top candidate in the fight to unseat Kentucky Senator Mitch McConnell next year.

Alison Lundergan Grimes, Kentucky’s secretary of state, announced Monday afternoon that she would challenge the Republican Senate leader, whose national clout belies his shaky standing at home. “Kentucky deserves a change,” she told supporters gathered in Frankfort, Ky., who whooped as she revealed a decision that was closely held until the moment she bounded onstage.

After a brief dalliance with actress and activist Ashley Judd, local and national Democrats zeroed in on Grimes, 34, as the best chance to topple the powerful five-term incumbent. A Lexington attorney and the daughter of a former state Democratic Party chairman, Grimes won election in November 2011, coasting to victory in the conservative commonwealth after tapping into a deep fundraising network. She ran in that race as a plainspoken, probusiness moderate, who put her grandmothers in a campaign spot.

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Her new target is a national heavyweight, one of the top practitioners of the inside game in either party and an architect of the GOP strategy to stymie Barack Obama’s agenda. While he is arguably the most powerful Republican in the country, McConnell is also, according to poll numbers, among the most vulnerable. A survey conducted by the Democratic firm Public Policy Polling (PPP) last spring pegged the Kentuckian as the most unpopular Senator in the country, with a lowly 36% approval rating. A more recent PPP survey found McConnell and Grimes deadlocked at 45% in a hypothetical matchup.

Even so, Grimes has a hard road ahead of her. McConnell may be unloved in Kentucky, but he has marshaled a powerful re-election operation armed with technological prowess and a well-stocked war chest. To shore up his right flank, McConnell recruited Jesse Benton, a former top adviser to Kentucky’s junior Senator Rand Paul, to run his campaign. His team showcased its tactical savvy last spring by redirecting criticism after rogue liberal operatives bugged his campaign office. The recording, which spurred an FBI investigation, left few scars on McConnell despite revelations that his team had strategized about ways to tar Judd as “emotionally unbalanced.”

Republican operatives will attempt to link Grimes to Obama in a state where the President lost by more than 20 points last fall. “Kentuckians have absolutely no reason to send Alison Lundergan Grimes to Washington to help pass the policies of a President whom they adamantly oppose,” said Rob Collins, executive director of the National Republican Senatorial Committee.

Grimes said she was up for the challenge. “I am no stranger to being an underdog,” she said, noting the weeks she spent weighing the decision should not be taken as a sign of reluctance or hesitancy. “Kentucky is tired of 28 years of obstruction,” she argued in halting remarks that attacked McConnell for voting against a minimum-wage hike while quadrupling his own net worth over nearly three decades in office.

Even before Grimes jumped into the race, she was the target of preemptive strikes by pro-McConnell forces. One Web ad, cut by McConnell’s campaign, spoofed the Democratic establishment’s attempt to cajole her to run, while a conservative super PAC bought TV time to tie Grimes to Senate majority leader Harry Reid and paint her as “Obama’s cheerleader in Kentucky.”

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The race could be one of the nation’s marquee Senate matchups next year, with the money and mudslinging to accompany the high stakes.