Freshman Rep. Tom CottonTom CottonArk., Texas senators put cheese dip vs. queso to the test Overnight Defense: Debate over Mattis heats up | White House releases military force rules Senate GOP to Obama: Stop issuing new rules MORE (R-Ark.) officially launched his campaign against Sen. Mark PryorMark PryorCotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm Top Democrats are no advocates for DC statehood MORE (D-Ark.) Tuesday evening in his hometown of Dardanelle, Ark., setting up one of the most closely watched Senate match-ups of the 2014 election cycle.

Cotton laid out an anti-Washington, anti-Obama message consistent with his hard-charging conservative views, blasting "crony capitalists" throughout the speech and tying Pryor to President Obama and his signature healthcare law, both of which are deeply unpopular in the state.

"It's time to say 'enough.' Arkansans need a senator who will stand with them and stand up to Barack ObamaBarack ObamaObama to appear on 'The Daily Show' with Trevor Noah Brian Williams slams fake news Obama: I absolutely faced racism while in office MORE, a senator who will say 'no more' to the crony capitalism, the giveaways, the reckless spending, the unfair taxes, the job-killing regulations, and the concentration of unaccountable, unconstitutional power in Washington," he said. "Arkansans need a senator who won’t just stand by and accept the status quo.  I will be that senator."

Cotton's announcement has been long expected. He's been mulling a run for months, and sources close to Cotton told The Hill last week that he'd made up his mind.

The former Army Ranger ripped Pryor, accusing him of abandoning Arkansas for his party.

"Mark's been running for office for almost 25 years. Every time, he says 'Arkansas comes first.' It’s not so. Over the last four-and-a-half years, for Mark Pryor, Barack Obama comes first," he said. 

"Mark Pryor is the reason ObamaCare is the law today. He could’ve stopped it, but he stood with Obama instead. Mark Pryor voted for Obama's wasteful stimulus that added almost a trillion dollars to the debt, without lasting job growth. Mark Pryor voted for Obama’s amnesty plan for illegal immigrants that will hurt Arkansas families by driving up unemployment and driving down wages, without securing the border. ... Mark Pryor doesn’t put Arkansas first any more — Mark Pryor puts Barack Obama first."

The campaign is expected to be a hard-fought one, and most observers view it as a must-win for the GOP if the party hopes to win back Senate control. A number of recent polls in recent days show a close race.