Kentucky Secretary of State Alison Lundergan Grimes said Monday she will run against Senate Minority Leader Mitch McConnell for his re-election bid next year, giving Democrats a long-awaited, high-profile challenger to the powerful Republican.

Grimes has been considered the Democrats' best hope to end McConnell's almost three decade-long tenure in the Senate since actress Ashley Judd decided in March not to run. The race is expected to be one of the most closely watched of the 2014 mid-term elections.

"Kentucky is tired of 28 years of obstruction. Kentucky is tired of someone who voted against [raising] the minimum wage," Grimes said while announcing her decision in Frankfort, the state capital. "Kentucky is tired of a senior senator that's lost touch with Kentucky issues, voters and values."

Grimes has served her current post since January 2012. She previously worked as a private attorney.

McConnell's seat is one of 14 that Republicans are defending next year, while Democrats will defend 21.

The Kentucky senator won re-election in 2008 with 53 percent of vote, defeating Democrat Bruce Lunsford.